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Title: Stray Feathers From a Bird Man's Desk
Author: Rand, Austin L.
Language: English
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STRAY FEATHERS
FROM A BIRD MAN'S DESK
STRAY
FEATHERS
FROM
A BIRD MAN'S
DESK
By Austin L. Rand
CURATOR OF BIRDS,
CHICAGO NATURAL HISTORY MUSEUM
WITH CARTOONS BY RUTH JOHNSON
DOUBLEDAY & COMPANY, INC., GARDEN CITY, N.Y., 1955
_Library of Congress Catalog Card Number 55-5254_
_Copyright, 1955, by Austin L. Rand_ ©
_All Rights Reserved_
_Printed in the United States_
_At the Country Life Press, Garden City, N.Y._
_First Edition_
CONTENTS
PAGE
Introduction 9
Birds Using Tools 15
Birds as Brigands 19
Birds Bathing 22
How Birds Anoint Their Feathers 25
Traveling Birds' Nests 28
Maladaptation in Birds 31
Feathered Baby Sitters and Co-op Nursery Nests 35
Birds' Nests and Their Soup 38
Walled Wives of Hornbills 42
Buried Eggs and Young 45
The Snowy Owl as a Trade Index 48
Monkey Birds 51
Bird-Made Incubators 54
Cormorant Fishing 57
The Shrike's Larder 60
Bird Flavors 63
How Many Feathers Has a Bird? 66
Last Year's Birds' Nests 69
Symbiosis--Animals Living in Mixed Households 73
Bird Apartment Houses 77
Bird Helpers at Nesting Time 81
A Name for a Boat 84
Weavers and Tailors in the Bird World 88
Social Parasites among Birds 91
Fish Eats Bird! 95
Crows Are Smarter Than "Wise" Owls 98
Tame Wild Birds 101
Birds as Pilferers 104
Hibernation in Birds 108
Snakeskins in Birds' Nests 111
Co-operation by Birds 117
Watchdogs at the Nest 121
Bird Guides to Honey 124
Oxpeckers 127
Wings in Feeding 130
Instrumental Music of Birds 133
Conditioning in Birds 136
Poisonous Birds 140
Kingfishers on the Telephone 143
On Identifying Sea Serpents 147
Conservation over the Telephone 151
Birds Washing Food 154
How Animal Voices Sound to Foreign Ears 157
Sight Identification 160
Green Hunting Jays Turn Blue 164
How Birds Use Cows as Hunting Dogs 167
Early Bird Listing 171
Battle of the Sexes and Its Evolutionary Significance 173
Water in the Desert 177
Bird Graveyards 180
Animal Gardens 183
Dropping Things 186
Learning by Birds 189
Can Birds Count? 192
Courtship Feeding 195
They Turned the Tables 198
Survival of the Unfit 201
Dust and Snow Bathing 204
Decoration in the Home 207
Curiosity in Birds 210
References 213
Index 221
INTRODUCTION
In looking back over the preparation of these sketches I feel as though
each evening I'd gathered up the bits and pieces left over from the
day's work and fashioned them into designs for my own amusement and the
edification of my family. Truly it's as though I'd used stray feathers,
fallen from the bird skins I'd handled, and fitted them together into
something of wider interest than the original.
Much of my work now is museum research, working with bird specimens
and books. In fashioning a research paper I always amass a great deal
more material, that is to say, information and ideas, than I am able
to use in it. In place of a lumber room I have a set of files with
index headings that range from Abundance and Age, through such headings
as Beauty, Feathering of Feet, Fictitious, Hysteria, Pterylography,
Social, Song, Tail Feathers, Valentine's Day, to Zoogeography. Here
I put the information that is irrelevant at the moment but too
interesting to discard. Its source is varied. Some has been accumulated
while studying specimens from localities as geographically separated as
Alaska, El Salvador, Gabon, Tristan da Cunha, Nepal, Negros, and New
Guinea; and while writing papers that range from describing new species
to discussing secondary sexual characters and ecological competition.
Some have been recorded while in the field on expeditions, trips that
ranged from two years in Madagascar, three expeditions in New Guinea,
and a season in the Philippines to trips nearer home from the Yukon to
Nova Scotia, Florida, and Central America.
Gradually information builds up under each heading, and new ones are
added. These items are too interesting to remain buried in the files.
They are things people want to know about. So I began to draft them
into articles for publication in the museum's monthly, _The Chicago
Natural History Museum Bulletin_. The response was gratifying. The
press picked them up and reprinted them. One was used in a Chicago
_Tribune_ editorial. Several were used in commercial radio programs.
Encouraged, I prepared more, soon overrunning the space available in
the bulletin.
Most scientific papers are not written to be read for enjoyment.
Conciseness as well as clarity are striven for, conveying certain
information in a small compass. The correlations made are often obscure
ones, appreciated only by scientists. Yet the material they contain
is often intensely interesting, and if these papers were written in
a more leisurely style, with more general correlations pointed out,
they would provide both interesting and entertaining reading. In a few
cases my own research falls in this class, and I've rewritten some of
my own papers with this in mind (_see_ "Battle of the Sexes and Its
Evolutionary Significance").
This collection of articles, if it were a painting, could be called a
conversation piece. Or it might be compared to a well-filled whatnot.
Each of the sixty chapters is an independent unit, illustrating some
facet of birds, their behavior, or our study of them. Some of the facts
may seem unusual or bizarre, but most of them are well known and well
documented. The thing that is new, if there is anything new, is the
setting in which I've placed them, the manner in which I've looked at
them. Taken as a whole, they touch on many different birds from many
different places in their less widely known aspects, and with a human
interest slant.
"But what will your professional colleagues say?" asked a friend as
he flipped through the cartoons. "These pictures don't approach the
subject in a very serious manner." Quite true. But a discipline must
be very lightly rooted indeed if it can't stand a few caricatures and
cartoons and perhaps be the better for them.
The knowledge of most people about the hornbills of tropical Africa,
the gulls of Australia, the penguins of Antarctica, and the crocodile
birds of the Nile is probably pretty vague. To give a frame of
reference in a biological sense is impractical in the compass of one
slim volume.
But a ready-made frame of reference already exists: the parallels in
bird and in human. These I have used. But in so doing I am not imputing
human motives and attributes to birds. The actions are similar. The
workings of the human mind I understand only vaguely; that of the
bird I can study only through the actions of the birds. One set of
behavior may be learned and rational, one rigidly innate, entirely
instinctive, and inherited, or at most modified by experience. Be that
as it may, the similarity in the end result in two such different
vertebrate animals as man and bird when faced with similar problems is
often close. Perhaps it is because the solutions are necessarily few;
perhaps, and I incline to this feeling, it helps illustrate one aspect
of the close relationship between all animate nature.
This series of articles is intended to be interesting and entertaining.
I hope it will also make more people aware of the many ways birds
act, here and in far places, how they have solved their problems and
profited by their opportunities.
STRAY FEATHERS FROM A BIRD MAN'S DESK
BIRDS USING TOOLS
[Illustration]
Man is the tool user pre-eminent in the animal world, but he does not
stand completely alone in this. Here and there, in quite different
groups of animals such as insects, mammals, and birds, a few kinds have
forged a little ahead of the rest of their near relatives and show the
very beginning of tool using.
The song thrush of Europe is perhaps a borderline case. It feeds in
part on snails. To get the soft edible animal out of its shell, it
carries or drags the snail to a favorite rock, its anvil, and there
hits it against the anvil until the shell is broken and its contents
exposed. The question is, can this be considered as using a tool? If
the song thrush moved or prepared the rock, which it does not do,
there would be no question that it was a tool. The sea otter brings
a stone from the bottom of the ocean and places it on its floating
body to use as a similar anvil in cracking hard objects, and this
undoubtedly is the use of a tool. At the other extreme are many species
of birds that beat their prey on branch or ground, wherever they happen
to be. The song thrush is certainly an advance over that, and can, I
think, be considered as using a tool in a primitive way.
A few other species, too, bring shellfish to special places. Gulls on
our coasts pick up mussels and clams and, flying over a rock or some
other hard surface, drop the shellfish, and follow it down. If the
shell is broken, the dish is ready for the gull; if the shell is not
broken the gull takes the shellfish up to a higher altitude and tries
again. In places where hard-surfaced roads are conveniently located
gulls have learned to use them as shell-breaking places, and such roads
become littered with shells.
Crows of more than one species also use the same routine in breaking
open shellfish, and they, too, have learned to use special hard
surfaces, such as masonry walls, on which to drop the shellfish.
PAINTING A BOWER The satin bowerbird of Australia, a species known to
science as _Ptilonorhynchus violaceus_, has also been considered as a
case in point when discussing the use of tools. The birds are somewhat
larger than a robin, the male glossy blue-black, the female greenish.
The male of this species constructs an elaborate bower, presumably for
courtship purposes. It makes it of sticks and twigs, and decorates it
with bright and curious objects such as shells, feathers, bits of
bone, and fruits, as do several other species of bowerbirds. But the
satin bowerbird is unique in painting the inside of its bower. Fruit
is crushed in its bill, and the bird, using its bill as the tool or
paintbrush, smears the fruit juice on the sticks on the inside of the
bower. While this is a wonderfully strange habit, and apparently unique
in the bird world, it is doubtful if this behavior can be considered as
using a tool. If the satin bowerbird used a twig, or a wad of moss or
fiber, which it does not do, in spreading the paint, the case would be
clear.
The clearest case is that of the woodpecker finch of the Galápagos
Islands. _Camarhynchus pallidus_ is its proper name. It is one of a
group of dull-colored finches restricted to the Galápagos Islands.
Before it became known that one species used a tool, the chief claim to
fame of the group was that it, along with some other Galápagos Island
animals, such as the giant tortoises, had a great influence on Darwin's
thinking which resulted in his working out the theory of evolution as
set forth in his _Origin of Species_.
The woodpecker finch feeds largely on insects it gets by searching
and probing on the ground, and on the trunk and leaves of trees. In
searching crevices the woodpecker finch is handicapped by its rather
short, thick bill, and to offset this, it picks up a slender, short
length of stick, or the spine of a prickly pear, and with this in its
bill, pokes into crannies. The insects, disturbed or driven out, are
seized. Sometimes the woodpecker finch digs into the tree trunk and
then gets a stick to probe with; sometimes it carries its probe about
with it, poking in crannies until prey is disturbed. Then the stick is
dropped and the food seized.
We have seen how several birds are perhaps borderline cases in
using tools. They use certain special aspects of their environment
in preparing their food, and use it time after time. It's probably
instinctive behavior, but learning is shown in the gulls and crows
coming to recognize and use a hard-surfaced road in breaking open their
shellfish. The use of a probe by the woodpecker finch is a clear and
unique case of tool using by a bird.
BIRDS AS BRIGANDS
[Illustration]
Anti-social activities of humans such as those of brigands who plunder
their fellow men find their parallels in the bird world.
The bald eagle is one of the best-known of the birds that practice
such brigandage. Fond of fish, and capable of capturing it himself
upon occasion, it is a common practice for the eagle to take fish from
the osprey, plunder the osprey has just caught from the water. The
osprey, with a fresh-caught fish, flies heavily. The watching eagle
quickly overtakes the smaller, heavily laden bird and forces it to
drop its catch, then dives down and usually catches the fish before it
can strike the land or water. Rarely does the osprey escape with its
food under such an attack. It is recorded that an eagle made several
dives at one fish-laden osprey and, when these were not successful in
making it lose its hold on the fish, the eagle dived under the smaller
bird, turned over on its back, and with talons outstretched, snatched
the fish from the grasp of the osprey and sailed away with it, as
successful a pirate as ever sailed the seas.
NEMESIS OF VULTURES Besides taking fresh-caught food from the osprey
the bald eagle has been seen pursuing vultures and making them disgorge
their meal of carrion. The eagle, if unsuccessful in catching the
disgorged food in the air, may land on the ground and eat it there.
We know also that the aerial flights the eagle uses to frighten the
vulture into relinquishing his food are not idle threats, for an eagle
has been seen to strike and kill a bird that refused to disgorge.
Not only does our American eagle adopt such practices, but related
species in other parts of the world behave in similar ways. The New
Guinea sea eagle harries the osprey there, and on the west coast of
Africa a sea eagle robs pelicans and cormorants of their prey.
Certain long-winged birds of the tropical seas, such as _Fregata
magnificens_, are known popularly as man-o'-war birds or frigate
birds, reflecting their well-known character as pirates and tyrannical
freebooters. The man-o'-war birds get part of their food from many
creatures which swarm at the surface of the sea, but they also get much
of their food by forcing terns, cormorants, boobies, and pelicans to
deliver up their catch.
In a tropical bay a school of small fish comes to the surface, perhaps
driven by large fish below; from far and near terns gather, darting
down to seize the fish that jump into the air. Above them circle the
frigate birds, ready to dive down and chase and harry a successful tern
until it drops its fish and leaves its prey to the freebooter.
BOOBIES ARE VICTIMS Frigate birds may sail about, also, where a colony
of nesting brown boobies is located, waiting for the birds laden with
food to return home. When such a food-laden booby returns, the frigate
bird dashes down at it, buffets it with its wings, snaps at it with
its long, hooked bill, until the booby finally drops its fish for the
man-o'-war bird to enjoy.
The skua, a big, dark relative of the gull, is also known as a pirate.
Its chief food is fish but it also eats many other foods from the
sea. It rarely takes the trouble to fish for itself but watches until
some other bird, perhaps a gull or a tern, has been successful in
its hunting and then gives chase, forcing the unfortunate hunter to
relinquish its food. Several of the skua's smaller relatives, the
jaegars, have similar habits. It is written of the pomarine jaegar off
our New England coast that they are notorious pirates and freebooters,
the highwaymen among birds that prey on their neighbors on the fishing
grounds and make them stand and deliver. The jaegar gives chase to a
tern that has caught a fish and follows it through every twist and turn
as if the two were yoked together. Finally the harassed tern drops its
fish and the jaeger swoops down and seizes it before it can strike the
water.
BIRDS BATHING
[Illustration]
The toilet of most birds includes wetting their feathers in water and
shaking the feathers and preening them with the bill. This bathing
probably helps remove foreign matter from the birds' plumage and
helps keep it in good condition. In addition it is probable that in
summer the birds derive enjoyment from the coolness resulting from the
bathing. But birds bathe in cold weather as well as warm and have been
recorded doing so when the temperature of the air was only 10 or so
degrees above zero.
The sparrows and robins that come about a birdbath usually hop right
into the water. They squat down, fluttering their wings, and duck their
heads into the water, splashing and rolling it over their backs. They
may become quite drenched. Then they fly to some perch to sit and preen
and dry their soaked feathers.
But some birds take shower baths. During a shower in late summer I have
seen marsh hawks sitting in the rain with wings spread, apparently
enjoying the wetting the shower gives them, and a buzzard has been
recorded as deliberately flying to an open perch in a rainstorm and
sitting there with its wings spread and sometimes shaking them until
the shower was over, when it flew to a sheltered place.
SPRINKLERS A BOON The artificial showers of lawn sprinklers provide an
opportunity for birds about our gardens to take a shower bath in fine
weather. A robin or a flicker may hop into the shower and squat there
and indulge in bathing antics on the wet grass. Hummingbirds have been
seen to fly into the dense spray of a lawn sprinkler and hover there
for a moment, gradually assuming a vertical position and spreading the
tail, then slowly settling to the ground, and finally "sitting" on the
grass, body erect and tail spread out fanwise, the wings continuing to
vibrate slowly. In a few moments the bird may rise into the air and
repeat the whole performance.
In wet tropical forest it is probable that many of the treetop birds
bathe in the water that collects on the surface of the leaves, pushing
their way through clusters of wet leaves and over wet surfaces of
others until they are as wet as if they had actually been bathing
in water. This is not restricted to tropical birds, for even in our
latitudes towhees have been recorded as bathing thus, and thrushes and
flickers have been seen to rub themselves over the wet grass and then
go through the actions of bathing followed by preening.
BATHING WHILE FLYING Watching swifts or swallows coursing low over the
surface of a lake and occasionally touching it leaves one with the
impression sometimes that the birds are bathing rather than picking up
insect food or drinking. With some other birds the habit of bathing
from the wing is more definite. Sometimes drongo shrikes that are
sitting up on a perch near the edge of a pool will fly out over the
water, drop directly into it with a little splash, and then rise and
fly back to their perch, where they either repeat the performance or
sit and preen their feathers.
POST-PRANDIAL ABLUTIONS Ospreys have been recorded as bathing while
on the wing in a rather striking manner. They have been seen flying
along just above the surface of the water, then descending into it,
adopting a sort of vertical American-eagle attitude while flapping the
wings, then rising a little, flying on, and repeating the process. It
has been suggested that the osprey is washing its feet in this manner
after finishing its meal. One observer makes this still more definite.
He says that the osprey finishes its meal of fish on a perch in a tree
and then flies low over the lake. Dropping both its legs, the osprey
drags them through the water, flapping its wings all the time. Then it
immerses its beak and head into the water while still flying along,
apparently washing off the scales and slime that it had gotten on
itself while making its meal of fish.
HOW BIRDS ANOINT THEIR FEATHERS
[Illustration]
A bird's plumage receives a great deal of care from the bird that wears
it. The bill is the only implement for this grooming, and it is run
through and along the feathers it can reach, helping clean them and
making sure they lie in their proper place in the bird's dress. There
are parts of the plumage that the bird's bill obviously can't reach,
as that of the head, but ducks at least surmount this difficulty by
rubbing their head against their body.
Many birds have oil glands (the only external glands that most birds
have), a pair of glands just above and in front of the root of the
tail, on the back. They contain an oily substance, and the usual
explanation of its use is that the secretion of these glands is used
in dressing the feathers. Certainly birds that have oil glands seem to
use them, nibbling at them as though to press out the oil, touching
them with the bill, and then rubbing the bill through the feathers, and
rubbing the head against the oil gland.
The beautiful, soft, whitish bloom seen on some birds' feathers, such
as the pale gray of a male marsh hawk and filmy appearance of some
herons' plumage, is caused by specialized feathers called "powder
down." Sometimes this powder down is scattered through the plumage;
sometimes it is in patches, such as the particularly conspicuous ones
in the herons. The tips of the powder down are continually breaking off
and sifting over the rest of the plumage, giving it the bloom that with
handling quickly rubs off.
WALNUTS AS A COSMETIC But birds sometimes rub foreign substances over
their feathers--just why we don't know. Grackles have been known to use
the acid juice of green walnuts in preening.
In Pennsylvania starlings have been seen to come to walnut trees when
the nuts were almost three-quarters grown, in June, and peck a hole in
the sticky hull of a nut, clip the bill into it, undoubtedly wetting
the bill against the pulpy interior, and then thrust the bill into
their plumage.
They did this from June to August, especially on hot, dry summer days,
but some birds continued this even during light rain. Some years before
the above was recorded, when this sort of thing was less known, Edward
Howe Forbush, noted ornithologist, cautiously used a similar record in
his classical _Birds of Massachusetts and Other New England States_. He
writes that his colleague, J. N. Baskett, says he saw a bluejay lift
its wing and rub pungent walnut leaves repeatedly into the feathers
beneath.
BEER AND MOTH BALLS Since then such things have been recorded a number
of times, including a catbird that anointed its feathers with a leaf
and a grackle that found a moth ball and, holding this in its bill,
rubbed it against the underside of its spread wing and the side of its
body. After several applications the grackle dropped the moth ball and
preened its feathers; then again it picked up the moth ball and treated
the other wing as well as its belly.
Recent experiments with tame song sparrows have shown that they may use
beer, orange juice, vinegar, and other things made available to them in
dressing their plumage, and it appears that this may be correlated with
a little-understood type of activity known as anting, in which live
ants are placed on the feathers.
TRAVELING BIRDS' NESTS
[Illustration]
In spring and fall many of our birds make long journeys under their own
power, some of the most publicized being the migration of the Arctic
tern, a bird that may spend the northern summer north of the Arctic
Circle and, before returning there next season, may have visited south
of the Antarctic Circle. The golden plover that makes a nonstop flight
to Hawaii is another famous traveler, and many of our smaller songbirds
are no mean travelers either. The barn swallow that nests about an
Illinois farm in the summer may spend the winter in Argentina. The tiny
hummingbirds' feat of crossing the Gulf of Mexico nonstop is worthy of
mention too. Such travels have become commonplace through familiarity.
We have come to accept even the possibility of occasional transatlantic
passages of small perching birds, helped by transatlantic vessels, and
of such birds as starlings, making their way from place to place by
boxcar.
But when it is time for birds to make their nests and rear their family
we expect them to give up their traveling for a time and to settle down
in one place. We expect, with our songbirds, to have the male arrive
first, pick out a territory, and announce to his species that other
males are to keep out and that a mate is welcome. The female arrives
and chooses her mate or territory, and a nesting ensues. Many species
defend the area around the nest against others of their kind. So it
comes as a surprise to find nests built in such a situation that they
are not stationary but move back and forth, along with part of their
environment.
BY BOAT Tree swallows nest on the ferryboats that ply between
Ogdensburg, New York, and Prescott, Ontario, across the St. Lawrence
River where it is more than a mile wide. The nests are tucked into
suitable openings on the ferries, and the frequent trips back and
forth across this mile of water and the docking at different piers do
not seem to disturb the birds. They gather their nesting material of
feathers and straws and leaves from either shore, and when the young
are being fed, insects may be gathered about the Canadian or the United
States shore, depending on where the ferryboat is docked.
Another example comes from Western Australia, also of a swallow, the
welcome swallow which is nearly like our barn swallow. A pair of these
birds nested on a boat used for visiting local coastal stations. If
there were eggs or young in the nest when the boat sailed, the old
birds would accompany it, once following her on a trip of thirty-five
miles and back.
BY TRAIN Barn swallows have been noted nesting on railway trains that
run across the two-mile portage between Atlin Lake and Lake Tagish in
British Columbia. In the summer the train makes the trip almost daily,
and for many years a pair, or a succession of pairs, has made its
nest and raised its young in one of the open baggage cars. Members of
the train crew took an interest in the birds and put up a cigar box
for a safe place for their nest. Here the family seemed to prosper,
undisturbed by the proximity of people and baggage and the clatter as
well as the movement of the train.
MALADAPTATION IN BIRDS
[Illustration]
Through selection birds have become adapted to their environment. In
most cases this is successful adaptation. Occasionally, however, we
come across instances in which the adaptations do not work out. Such
cases, where the actions of the birds are not beneficial or are even
detrimental to it, come as surprises.
Since the introduction of the Tartarian honeysuckle (_Lonicera
tatarica_) into the United States from Asia, its planting as an
ornamental shrub provides each autumn a display of juicy red fruit.
This fruit contains saponin, a substance that has the effect of an
anesthetic and muscle poison and may paralyze the greater nerve
centers (in sufficiently large doses saponin causes death by cardiac
paralysis). A condition of intoxication has been recorded for robins
feeding extensively on these honeysuckle berries: "... this drunkenness
has been seen in every shade of severity, from mild unsteadiness to a
degree of incoordination sufficient to cause the birds to fall to the
ground. It seems to make some of the birds utterly fearless and perhaps
a bit belligerent, for they become quite unafraid of passers-by and
interested spectators. A few dead robins have been found about these
honeysuckle bushes--presumably poisoned by the berry diet." Fortunately
the poisoning of birds by this honeysuckle seems to be uncommon.
In the Philippines the local people gather the juice of the coconut
inflorescence in bamboo tubes placed in the crowns of the palms. This
juice ferments quickly and provides a refreshing, mildly intoxicating
drink. A little parrot of the Philippines, the hanging parakeet, has a
taste for this drink, comes and drinks from the containers, sometimes
becomes drunk, falls in, and drowns.
The California woodpecker ordinarily differs from many birds because
it does not lead a hand-to-mouth existence but stores food. These
woodpeckers feed extensively on acorns, and one way they store them is
by drilling holes in the bark of a tree and fitting an acorn into each
hole. The whole trunk of a tree thus may be pitted with stored acorns.
When the acorn crop fails and the nuts are scarce the woodpecker
goes through the same storage activities but, being unable to find
sufficient acorns, it stores pebbles instead. These pebbles are, of
course, quite useless to the woodpecker, and this is an interesting
example of an instinct "gone wrong."
Sometimes these woodpeckers have another method of storing their
acorns. This is by dropping them into cavities in tree trunks, but when
stored in such a way there seems to be no way for the birds to reach
them. Here again we have a blind impulse to store acting in such a way
that the bird gains nothing by the act.
The raven is ordinarily and quite correctly considered one of the most
intelligent of birds, but a raven I kept in captivity and fed small
fish attempted to store some of them by pushing them through a knothole
in the back of its cage. The fish fell about fifteen inches below the
knothole, where the raven could not possibly reach them. After pushing
each fish through the raven peered through the knothole though it
could not see the fish. Here again we have the instinctive storing act
carried out in such a way that it produced no benefit to the bird.
The late George Latimer Bates, noted ornithologist, studying the birds
of West Africa, found a most surprising thing in connection with one of
the honey-guides. As a group, these birds are noted for the habit of
attracting the attention of human beings and leading them to bee trees,
presumably so that they will break down the bee tree for the honey, and
the birds can feed on the scraps left over. Bates found that the West
African species is parasitic on other birds in its nesting habits and
its young have been found in the nesting hole of a little barbet. This
barbet was a much smaller bird than the honey-guide and the entrance
to the nest hole was so small that Bates doubted that the honey-guide
would have been able to get in to lay its egg. He suggested that the
egg may have been laid elsewhere and deposited in the nest by the
parent's bill. It is difficult to understand how the young honey-guide
would be able to get out, for when fully fledged it would have been far
too large to squeeze through the entrance that admitted the tiny body
of its foster parents, the barbets. This is an almost incredible story
and if true looks like a case of maladaptation.
FEATHERED BABY SITTERS AND CO-OP NURSERY NESTS
[Illustration]
Co-operative nurseries, where a few parents look after the young
while the rest of the adults, temporarily freed of the care of their
offspring, can go about their other affairs, appear in the bird world.
The wild turkey of our Eastern United States commonly steals away
singly to lay its eggs and incubate them in its nest on the ground.
But occasionally it happens, Audubon writes, that several hen turkeys
associate together and lay their eggs in one nest, and raise their
young together. With the turkey apparently there is little division of
labor, as Audubon writes of finding three hens sitting on forty-two
eggs, but he says that one of the hens is always on the watch at the
nest so that natural enemies have no chance to rob it.
A GREGARIOUS BIRD What is of only occasional occurrence in one
species may be the regular course of events in another, and in the
ani we find it customary for a number of birds to nest together. The
anis are moderate-sized cuckoos living in the tropical Americas. The
smooth-billed ani is perhaps the best known, for Dr. D. E. Davis, when
studying at Harvard for his doctor's degree, made a special trip to
Cuba to study them in the field. The smooth-billed ani goes in flocks
the year round. Usually there are about seven birds in the flock, but
there may be as many as twenty-four. The nest is a bulky structure
of twigs and fresh leaves. When nest building starts usually one
bird is most active, but as many as five birds were seen carrying in
sticks at one time. When the nest of sticks and leaves is finished
several females may lay their eggs in it. But apparently only one bird
incubates at a time, and the male takes his turn at incubating. When
the young hatch, after about thirteen days, most of the adults in the
colony help feed the young.
Eider ducks may nest in dense colonies, but each bird has its own nest
in which it lays its own eggs, and in which the female alone incubates.
But after the young hatch and the mother leads them to the water, the
young may band into larger flocks, accompanied by a number of females,
and the young seem to be independent of their particular parent, but
attach themselves to and are tended by the nearest duck.
PENGUIN SOCIAL GROUPS A much more elaborate system for caring for
the young has been evolved by certain penguins. The sexes alternate
in their care of the young in the early stages. But when the young
are partly grown the family unity breaks up for a communistic type
of social organization. The young are now grouped into bands of up
to twenty or more birds and are left under the care of a few old
birds, while the rest of the adults go to the water, which may be
some distance away. Periodically they return with food for the young.
Apparently the individual young is not recognized by the parent, which
goes to the particular group of which its young is a part, and there
may feed any one of the "child groups."
Here we have two definite cases of a social organization that has
resulted in division of labor: in the incubation of the ani, and in the
care of young penguins. In addition we have two less specialized cases
of the same thing, showing the sort of raw material on which evolution
can operate to produce new behavior patterns.
BIRDS' NESTS AND THEIR SOUP
[Illustration]
In caves near the ocean in the Far East nest myriads of tiny swiftlets
whose chief impact on the civilized world is that their nests provide
an edible article of commerce. "Birds' nest soup" at once comes to the
mind of the Occidental, few of whom have ever eaten of the nests, or
even seen the birds to know them. For those who would like to see the
nests, some museums have them on exhibition, such as in the Chicago
Natural History Museum, where two nests are placed in their natural
setting, and beside them is a quantity of the material of commerce in
its raw state.
The birds themselves are dusky-colored swifts only a few inches
long, and belong to a group of swifts that represents perhaps the
most puzzling problems of species identification in the bird world.
As yet we do not know even how many species there are. The genus is
called _Collocalia_. Only some of its members make the edible nests;
others mix so much moss into the nest that it is useless for soup. One
species has the scientific name of _esculenta_, given in reference to
the supposed edible nature of the nest, but through error the name was
applied to a species whose nests are not edible. In habits all these
swiftlets seem very similar, flying about with a rather weak flight for
a swift, catching their insect food on the wing.
A number of swifts, including our chimney swift, use the secretion of
their salivary glands as a glue to stick together their nest, and to
stick it to the wall of a cave, the inside of a hollow tree, or the
inside of a chimney. But some of the edible-nest swifts go further
and make their nest entirely of this secretion from their enormously
enlarged salivary glands. This material, as it comes from the mouth
of the bird, resembles a saturated solution of gum arabic and is very
viscid. If one draws out a strand from the mouth of the bird and sticks
it on a rod, by rotating the rod and winding up on it the thread of
saliva one can empty the salivary glands of the bird. This material
dries quickly, and is the material of which the nest is made. When
the bird makes its nest, which it does in large colonies in caves,
it flies up to the rock wall, applies the saliva to the rock in a
semicircle or horseshoe. Gradually a little shelf is built out, and in
the finished nest one can see the many little strands that have gone
into the structure. It may take the birds as long as three months to
make this nest, even if undisturbed. The birds lay their two eggs in
the nest, and raise their naked, helpless hatchlings into facsimiles of
themselves in it.
But in the Orient, especially in China, the nests are highly prized by
epicures as a delicacy. As the supply is limited the price is high. A
note with some material we saw stated that the price was $12 to $36 a
pound in Siam.
The climbing for and collecting of these nests requires daring, skill
and is not without danger. The nests may be far back and high up in
the cave. Ropes and poles may have to be fixed in place to aid the
climber, who has a flaming torch in one hand and carries a sack or
basket for the nests. In Siam, at least, the collecting of these nests
was hereditary, father training son. The rights to collect nests are
valuable. In Siam, where the rights to collecting the nests were vested
in the state, revenue of as high as £20,000 has been received from the
rights for this collection.
The nests are said to be of highly nitrogenous material, and contain
about 50 per cent of protein and 7½ per cent of mineral matter. Their
use as food is an Oriental custom, but an Occidental opinion of their
flavor is that it is bland, and an appreciation of it needs to be
cultivated. The price of these nests is so great that unscrupulous
persons have manufactured spurious nests. These nests are made from
agar-agar, the jelly made by boiling down certain seaweed, and are so
cleverly flavored that only connoisseurs can detect the fraud.
We usually think of these nests in connection with birds'-nest soup,
which may be made with chicken or beef broth and then the cleaned
material of the nest added like tapioca or vermicelli. Sometimes a
sweet soup is made. Sometimes lotus seeds, sugar, and the nest material
are used in the preparation of the dish. But in the Orient, at least
formerly, they're considered to have medicinal qualities, too. It is
said that when combined with ginseng they are capable of restoring life
to a person on the point of death. In Northern China where the winter
is bitterly cold, it is a general belief that the blood congeals and
can only be thawed out by drinking a soup made of these nests. The
list of further benefits, such as against tuberculosis, as a tonic,
stimulant, and a pacifier of the stomach, recall advertisements of
patent medicines.
WALLED WIVES OF HORNBILLS
[Illustration]
For long it has been written that the male hornbill walled up his mate
in her nest in a hole in a tree at nesting time, and one author even
wrote that the male plucked out the female's feathers at this time.
The facts underlying these statements have different interpretations,
but the nesting of the hornbill is still one of the most extraordinary
of animal habits. Travelers and naturalists in Africa had brought back
tantalizing bits of information, to add piecemeal to our knowledge of
these birds. Now all this is synthesized and corrected by R. E. Moreau,
onetime resident in East Africa, who made a study of certain species,
raised young birds by hand, and gave us a comparative study of their
behavior. Even this study must be considered preliminary, for, of the
twenty-six African species, we have breeding data on only sixteen of
them.
First we must not generalize too far as to "the hornbills," for there
are Asiatic and Malayan species as well as African, and African species
differ among themselves, the ground hornbill being especially aberrant
in its habits.
It is quite true that in many African species the female is walled up
in her nest, and the period when she is enclosed may last three to
four months. But it cannot be interpreted as an imprisonment forced on
her by the male, and presumably she could, if she wanted to, open the
entrance at any time, as she does finally on emerging.
Among the African species the details vary, but the nest is usually
located in a hole in a tree, and except in the case of the ground
hornbill the entrance is plastered up so that only a narrow slit is
left, about wide enough for the passage of the bird's bill. The female
takes an active part in the walling up of the opening, and might be
said to wall herself in. When the opening to be filled in is wide, the
male may bring earth, which he mixes with saliva in his gullet, and
presents to the female, who does the actual plastering. In some species
the walling up of the entrance may take months.
The female may wall herself in some days before she lays her first egg.
Throughout incubation she remains there. Depending on the species, she
may peck her way out, or burst out when the young are partly grown, or
she may stay until the young are ready to fly.
During the time the female is walled in the male brings food for her,
and later for the young, also. That he is a good provider is indicated
by the fatness of the female and her young. This is proverbial with the
natives of Africa. The method of feeding varies with the species. The
male may bring a bit of food in its bill, pass it in to the female,
and then go for another, or in other species we might think more
intelligent, the male carries a quantity of berries in its gullet, and
these are regurgitated one by one and passed to the waiting female;
such species make trips to the nest less frequently.
Apparently shortly after the female goes into the retirement of her
walled-in nest, she molts all her flight feathers, so that she is
flightless, and then begins to grow them again.
When the female bursts out of the nest with the young only partly
grown, the young that remain in a still very undeveloped state in the
nest, using material in the nest such as remains of food and rotten
wood, replaster the hole! The young, perhaps only halfway through their
fledgling period, wall themselves in! The female then helps the male
care for the young.
Such is an outline of what some of the African hornbills do at nesting
time. The habit is unique in the bird world. One species appears not to
wall up its nest. In an Asiatic species it is said that if the male is
killed other hornbills help to feed the female in retirement. The whole
procedure is an amazing behavior pattern, and one for the development
of which it is difficult to find a functional explanation.
BURIED EGGS AND YOUNG
[Illustration]
The crocodile bird, or Egyptian plover, has enjoyed a dubious publicity
because of its reputed habit of entering, and coming out of, crocodile
mouths. As Herodotus put it, the crocodile's mouth is infested with
leeches, and when the crocodile comes out of the water it lies with its
mouth open facing the western breeze. Then the crocodile bird goes into
the crocodile's mouth and devours the leeches, to the gratification of
the crocodile, who is careful not to harm the bird. Though there are
some more recent observations corroborating this, modern observers who
have had abundant opportunity have watched for this behavior and have
not seen it.
As one authority on African birds puts it, it is evidently not an
everyday occurrence.
But the crocodile bird has other habits that are just as bizarre and
interesting. It lives along the sandy shores of African rivers, and
when it lays its clutch of two to four eggs these are buried in the
sand so there is no sign of them aboveground. The bird sits on top of
this spot. A. L. Butler, who studied this bird in the Sudan, thought
that the sand might be scraped away from the eggs and the eggs brooded
in normal fashion by night. The young birds are very precocial, and
feed themselves on tiny insects, but they follow the parent. When
danger threatens the young squat motionless in some depression. The toe
mark of a hippopotamus is a favorite place. Then the old bird, with her
bill, throws sand over the young until they may be completely covered.
Not only does this happen when the birds are very small, but continues
up until the time the birds can fly. Dr. W. Serle in Sierra Leone once
saw a crocodile bird burying something and found the disturbed spot
fairly easily, as recent rain had beaten the sand beach smooth and
hard; a fully fledged young was unearthed. It squatted motionless until
prodded from behind, then it ran swiftly, rose, and flew away strongly.
The burying is not only protection from immediate enemies; A. L. Butler
believed it was normal for the young when not feeding to be buried for
safety or as protection from the burning sun. For a further protection
from the sun the parent moistens the sand by regurgitating water over
it.
Butler on one occasion saw a crocodile bird drink at the water's edge,
run up onto a sand beach, regurgitate water, then settle to brood.
Butler marked the spot, went to it, and, scraping away the dampened
sand, found a tiny chick about one inch below the surface.
This covering of the eggs by the parent is not unique in the bird
world. The pied-billed grebe of North America also does this. When
disturbed at the nest the incubating bird has been seen to use quick
pecking motions to draw material from the edge of the nest over the
eggs. Instead of leaving the eggs exposed the nest simply looks like a
heap of trash and may thus escape the attention of a predator. It used
to be thought that this grebe used to incubate only at night, leaving
the eggs covered during the day to be incubated by the heat from the
sun and from the decaying vegetation of the nest. However, recent
studies have shown this is not the case, and protection by concealment
seems to be the main advantage of this behavior.
Yet another species of quite a different group, the eider duck, covers
its eggs on leaving them. The eider's nest is characterized by a
blanket of down, plucked from the breast of the bird, and when the
female has time, when she leaves the nest she pulls the edges of the
down blanket over the eggs, perhaps for concealment, perhaps for the
sake of the down's insulating properties, keeping the eggs warm in a
northern climate during the parent's absence.
Here we have covering of eggs for what seems to be very different
purposes: to keep the eggs cool; to keep them warm; and to hide them
from view.
THE SNOWY OWL AS A TRADE INDEX
[Illustration]
Angus Gavin was a fur trader at the Perry River post of the Hudson's
Bay Company on the edge of the Arctic Ocean. White foxes were the
chief fur brought in, and the Eskimos were the trappers. Sometimes it
was necessary to advance credit to an Eskimo, against the expectation
of a coming season's catch out of which the advance was to be repaid.
Gavin, who was a keen naturalist as well as trader, writes, "I used my
observation on Snowy Owl abundance to govern extension of credit...."
When snowy owls were abundant he could extend liberal credit to the
Eskimo with every assurance the white-fox catch would be good and that
the Eskimo would be able to liquidate his debt. When snowy owls were
scarce little credit would be extended, for the white-fox catch would
be small.
In general we've accepted the value of birds to man, and are
appreciative of the complicated web of life in which one animal affects
many others. But this use of snowy-owl abundance as a guide in granting
credit strikes me as novel. Actually, of course, it is quite sound, for
it uses one part of the chain that links such diverse items as owls,
lemmings, foxes, Eskimo, fur trader, and finally of course milady in
her white-fox furs.
LEMMINGS IMPORTANT First of the factors involved is, of course, the
vegetation; the grasses, herbs, and tiny dwarf shrubs of the Arctic
barrens. The next are the lemmings, mouselike creatures of the Far
North that eat the vegetation. They are the first step in turning
grass into flesh and fur and feathers. One of the striking facts of
lemming biology is the fluctuation in their numbers. Some years they
swarm, lemmings are everywhere, and in places they erupt in vast
emigration, the tundra and the sea ice being covered with masses of
moving lemmings. We know this best from the accounts written about the
lemmings of Norway, but the same thing occurs in the American Arctic.
At other times they're scarce and it is difficult to find even one.
Strangely there's a periodicity in this, and periods of abundance and
scarcity tend to recur every four years. What happens or what causes it
we don't know.
The Arctic fox, staple fur bearer of the Far North, and the snowy owl
both prey on lemmings. Lemmings are so important to them that when
lemmings are abundant the foxes and the owls prosper and multiply; when
the lemmings are scarce the foxes and the owls starve or migrate, in
any case where there are few lemmings there are few foxes or owls.
Thus we see how it is that an abundance of snowy owls can indicate
that the Eskimo will make a good fox catch and the trader will do good
business.
MONKEY BIRDS
[Illustration]
Birds get their everyday names in a variety of ways in the countries
where they live; from their looks, like the snake birds and the pond
scroggins; from their color, like the cardinal and the blackbird;
from their behavior, like the frigate bird and the creepers and the
boobies and king-birds; from what they eat, or are supposed to eat,
like the antbirds and plantain eaters and bee eaters; from what they
say, like the poor-will and the more-pork; from how they say it, like
the warblers and the screamers; from how often they say it, like the
brain-fever bird and the wideawake terns; from where they nest, like
the cliff swallow and the house martin and the chimney swift; and some
from their non-bird associates, like the cowbird, moose-bird, and the
monkey bird.
It is the monkey birds that have taken our fancy at the moment. The
forests of Africa, the jungles of Borneo, and the forests of the
Philippine Islands each have a bird that associates so often with
monkeys that this habit became incorporated into its local name. The
birds are not at all closely related. One is a hornbill, one is a
drongo shrike, and one is the fairy bluebird. The hornbill goes in
parties of their own kind, but apparently the drongo, and certainly the
fairy bluebird prefer the society of monkeys to that of their own kind.
The stories we have of them stress the utilitarian aspect of the
association; that the monkeys as they travel about through the trees
scare insects out of their hiding places and the birds, being on hand,
can snap up the insects more easily than if they had to search them out
for themselves.
The monkey bird in Africa, which is a hornbill, follows, along below
the monkeys in the lower branches of the trees. It used to be thought
this was for the fruit the monkeys dropped, but then it was found the
hornbills were insectivorous. Instead of being scavengers the hornbills
are using the monkeys to beat out their game for them.
Hamba Kerah, the slave of the monkeys, is what the Malays of Borneo
call the racket-tailed drongo. This is from its habit of stationing
itself behind a band of monkeys traveling through the forest. But Mr.
Ridley, who watched them, decided it was the other way around; the
monkeys, unwittingly of course, were working for the drongo, acting as
beaters to drive out the insects which the bird snapped up in the air.
In the Philippines it is "the sentinel of the monkey" that is applied
to the fairy bluebird. The bluebird seldom associates with its own
kind, but is almost invariably associated with a band of crab-eating
macaques. But here again it seems the monkeys are acting as beaters for
the bird, driving out insects.
This is a sort of unconscious co-operation one finds in the bird world.
One animal helps out another without being aware of it. Birds are ever
ready to profit by such behavior, and when it proves of enough benefit,
the habit can become usual for the species, as in the cowbird-cow
relationship, or indispensable as with the oxpecker-hoofed-animal
association.
BIRD-MADE INCUBATORS
[Illustration]
Incubators as we know them on chicken farms are electrical gadgets with
thermostats to control the temperature, or at least with oil lamps
to supply the heat necessary for the young chick in the egg to grow.
Naturally we wouldn't expect anything so artificial as this in the bird
world, but there is one group of birds that does not brood its eggs but
has employed another method of incubating.
The birds that do this are fowl-like birds of the Australasian area.
They are variously called "mound builders" from the nest mound they
construct, "megapodes" from the large size of their scratching feet, or
bush turkeys, presumably from their edible qualities. These birds bury
their eggs and leave them thus to hatch without any brooding by the
bird. The birds have adapted their habits to two different sources of
natural heat. On some of the Pacific islands there is local volcanism
making the sand warm. To such places the birds come to bury their eggs.
But in many of the tropical forests there is not this convenient
natural heat. Another method is employed. The birds take advantage
of the heat generated by rotting vegetation. They scratch up the
surface litter of the forest floor into mounds--structures that may
be a yard or two high and five or six yards across. Some much larger
have been observed. It is into these the hens burrow and lay their
eggs. The temperatures in them have been recorded as 95° to 96° F.,
which compares with normal bird temperatures of just over 100° (bird
temperatures are a few degrees higher than normal human temperature).
The bush turkeys from Queensland have been bred in captivity, and have
given some extremely interesting data, according to an article by Mr.
Coles in the proceedings of the Zoological Society of London for 1937.
It was the male who did all the building of the mound. Though the
female started to cover the eggs laid singly in burrows in the mound,
the male finished this. And it was the male that looked after the nest
mound during the incubation period, continually scratching over the
surface layer. Both parents helped the young emerge, by digging burrows
into the mound which the emerging young, who had started to burrow out,
could use.
The young are in a very advanced state and apparently are able to fly
and look after themselves upon emerging. On the day after hatching one
chick is reported as able to flutter up to a perch six feet high.
In the captive birds mentioned above, the parents, though they were
attending to the mound and helped the chick out, appeared to take no
further interest in the chick once it was out.
There are a few other cases when birds cover or bury their eggs. With
the grebes it has been said they covered them and left them to be
incubated, but that is doubtful. Certainly the megapodes are the only
ones to present a dear case of "artificial" incubation.
This burying of eggs by the megapodes of course brings to mind the way
some reptiles, such as turtles, bury their eggs. And considering that
from an evolutionary viewpoint birds are really only modified reptiles,
it is perhaps not surprising that they too have this habit. But that
it is really an ancestral trait retained by the megapodes is doubtful.
Rather I'm inclined to think it's another example of the many ways
birds have evolved, or changed their habits so as to utilize as much of
the environment as they can in as many ways as possible.
CORMORANT FISHING
[Illustration]
In western Europe, when falconry was in favor for taking game on land
and in the air, there was a certain vogue for training cormorants to
take fish. Like the falcons, the cormorants were hooded and carried
on the wrist, but of course where the falcons flew to their game, the
cormorants swam to theirs.
It was in China where cormorants were domesticated, "completely and
perfectly," as that eminent Sinologist Dr. Laufer says. Extensive
breeding establishments have been maintained. The eggs of the breeding
flock of cormorants are given to a hen to hatch, for cormorants as
mothers prove unsatisfactory under domestication. When the eggs hatch
the young cormorants must have special care; for, unlike the young of
ducks and geese, young cormorants at hatching are not down-covered
and able to run about, but are weak, helpless things sensitive to
cold. They are placed in cotton batting, artificial heat provided when
necessary, and they are fed by hand on a diet composed basically of
chopped eel.
Finally the young are full grown and fully feathered. The training is
now started. First the young are tied to a stake at the water's edge.
A whistle signal is given and the young cormorant is pushed into the
water. Thus he learns to know and obey the signal to go into the water.
Then the trainer throws him little fish. These the cormorant catches
in its beak and when he does the trainer whistles another signal, to
bring the bird back to him with the fish. And the cord tied to the
bird is used to demonstrate what is meant and make sure its done. So
the training goes on until the bird has graduated to a class taught
from a boat. Sometimes a small float is attached to the cormorant by
a short cord, and it can be drawn in with a bamboo hook. If young
birds are trained in the company of trained birds, it takes but half
as long. Finally the training is complete and the fisherman sets out
with his birds. This is no sporting event; it is the serious business
of life, getting a living from fishing. On the sampan or the bamboo
raft there may be from two to a dozen birds; sometimes they may have
special perches built for them along each side of the boat. Sometimes
the cormorant has a cord or band around its neck. The reason for this
is disputed. Some say its a place to attach a cord; a place to get hold
of the bird; some say each man's cormorant is thus specially marked for
identification; some that it's to prevent the bird from swallowing
its prey. With well-trained cormorants it is sometimes dispensed with.
At a signal the cormorants go into the water, swim, and dive seeking
fish. The fisherman, by stamping his feet, by voice or whistle, and by
hitting the water with a bamboo directs and encourages the birds. When
the cormorant catches a fish it brings it back to the boat, and the
fisherman may use a net, or may lift up the cormorant onto the boat
on an oar or pole, and take the fish from the bird. If a bird is lazy
it's encouraged by beating the water near it with a bamboo pole. As
cormorants' plumage is only partly waterproof they cannot stay in the
water indefinitely, and this, as well as fatigue, probably determines
the rest periods when the birds are lifted aboard. Sometimes the
fisherman helps attract fish to the boat for the cormorants to catch by
scattering grains of rice in the water.
When the day is finished the cormorants are collected, fed, and the
fisherman goes home with the sustenance for his family, gathered by a
bird.
In Japan the cormorant is also used, but apparently somewhat
differently. There cormorant fishing may partake of the nature of a
sport. Sometimes the cormorants are "harnessed" into a team, each
attached by a cord to a single line, directed by one master. In China
the fishing is usually done during the day, but in Japan night fishing
is common, the scene being illuminated by fires in braziers or cressets
on the boat, or lanterns.
THE SHRIKE'S LARDER
[Illustration]
Our northern shrike is a songbird which has developed feeding habits
along the lines of those of a hawk. Whereas most birds its size are
content with fruits, seeds, or insects of a size it can beat or bite
and then swallow whole, our northern shrike takes not only small
insects but prefers large ones, and mice and birds too big to be
swallowed whole. It is an opportunist and takes what is most abundant
and easily accessible. The shrike's strong hooked bill is a powerful
weapon, used with a nipping motion that is directed at the back of the
head or neck of mouse or bird.
Now with the dead sparrow or mouse the shrike is at a disadvantage.
With a powerful bill hooked at the tip its feet are still those of a
songbird and are not strong enough to hold its large prey while pulling
it to pieces. Only small insects are held in one foot and pulled to
pieces. To meet this need for holding large dead prey the impaling
habit was evolved. The result of this is the so-called larders, which
form a fancied resemblance to meat hanging in a butcher shop, and have
given the birds their name of butcherbird. A thorn tree, a splintered
end of a branch, or even the barbs of wire fencing may serve. The
shrike flies to one of these, carrying the prey in its bill (rarely in
its feet), and with a pulling motion fixes the prey on a projection
point. Sometimes instead of impaling the mouse or bird it pulls it into
the fork of a branch, and so wedges it there. Now the food is firmly
held, and the shrike can use its bill effectively to pull off pieces
of flesh and swallow them. When the bird has fed, it leaves the rest
of the animal hanging where it was. It may return to this food and
make repeated meals of it if not spoiled, or dried up, until the whole
is devoured. But often parts of meals are left hanging and discarded.
If suitable thorn bushes are scarce the shrike may return time after
time to the same tree with its prey, and in time this tree may come
to be decked with many partly devoured carcasses. Such trees are the
so-called "larders." There is another aspect of shrike behavior that
adds to these larders. The shrike, even when replete, may seize any
prey that appears and impale it. The bird's organization is such that
the sight of a small moving animal may start the actions that end with
impalement even when the bird is not hungry. This food usually is not
eaten later.
Thus the shrike's "butcher shop" is not primarily a store of food,
even though it sometimes serves as such when in times of scarcity
remains of old meals are eaten. It is not a gathering of food in time
of plenty and saving it for a later use. Rather the placing of many
items in one tree is the result of its being a favorable impaling
place. And the impaling is behavior developed to overcome the weakness
of the claws in a bird whose disposition and strong beak enable it to
prey habitually on larger animals which otherwise it could not tear to
pieces and eat.
BIRD FLAVORS
[Illustration]
Particularly in the study of insects it has been shown that bright
or contrasting and conspicuous colors tend to be associated with
ill-flavor in the animals that wear them, while insects with a good
flavor tend to be so colored that they are difficult to see. The
first is a warning coloration--advertising to a predator that he will
not enjoy eating this insect and better leave it alone; the other
is concealing color, its function apparently to keep predators from
finding their prey. The tasters in the experiments that have been
used to work out the above generalizations were usually birds, but,
as checks, a variety of other animals were used, and the magpie moth
(_Abraxas grossulariata_), for instance, was found to be distasteful
to certain spiders, frogs, lizards, various birds, a bat, and finally
"the late Dr. Hans Gadow (one of the leading ornithologists of his
day), who made a practice of sampling caterpillars, remarked on trying
an _A. grossulariata_ that it was quite one of the worst he had ever
eaten!" Apparently ideas in taste are similar throughout large sections
of the predatory animal world. Reversing the usual role, and using
insects (hornets) as tasters of bird flesh, the celebrated British
naturalist, Dr. H. B. Cott, has recently studied the question of
the palatability in birds and their coloration. Naturally Dr. Cott,
with his customary thoroughness, compared hornets as tasters with
other animals, including cats and men, and found a surprisingly close
agreement in the results.
The experimental procedure was to expose the flesh of two different
birds (without feathers) at the same time, and see which the wasps ate
first. Thus a graded series was built up of the 38 species of birds
tested, with a palatability rating of from 1 to 38. The wryneck and the
crested lark stood at the top of the list, and the pied kingfisher and
the white-rumped black chat, as the least palatable, at the bottom with
Numbers 37 and 38.
Then, surveying the coloration of the birds, and their habits, Dr. Cott
made the important correlation that in general the birds whose flesh
was most edible were protectively colored, and those whose flesh was
least palatable tended to be conspicuous in color and behavior!
To relate it to the theory of evolution Cott concludes that selective
pressure by predators seems to have forced vulnerable species along
two divergent lines of specialization: leading in those which are
relatively palatable toward concealment, and in those which are
relatively distasteful toward advertisement.
HOW MANY FEATHERS HAS A BIRD?
[Illustration]
The question as to the number of feathers on a bird seems a simple
one without complication. Dr. Wetmore, the well-known ornithologist
who was secretary of the Smithsonian Institute, has given us some
data. The number varies with the species, of course: the smallest
bird, a hummingbird from Cuba, had the fewest, 940 feathers; larger
birds had more, the robin 2587, and the mourning dove 2635 feathers. A
glaucous-winged gull had 6540; a mallard 11,903 feathers; a Plymouth
Rock chicken was said to have 8325 feathers; and a later investigator
reported 25,216 feathers on a swan.
But as one thinks of it, more questions arise, as in any
investigation. The answer to one question poses two more. The first
question is, do not the birds in winter need a wanner plumage to keep
out the cold than they do in summer, when it is warm? Do they have more
feathers then? This was definitely true in the case of the goldfinch:
a bird in summer dress had only 1439 feathers, while one in winter
plumage had 2368 feathers, obviously an adaptation for cold weather.
The next question is more abstruse, but eminently practical: the
smaller a body, the larger exposed surface for its weight it presents.
That is, for its weight a small bird has a proportionately much greater
surface from which heat is lost than does a larger one. With equal
heat-producing mechanism and metabolism, a small bird would need
more insulation than a large one. Reduced to its simplest: one would
expect small birds to have relatively more feathers than large ones:
more feathers per gram of weight. Is this true? Two members of the
Department of Poultry Husbandry at Cornell University, Dr. F. B. Hutt
and Lelah Ball, supplied the answer. Small birds do have more feathers
per gram of body weight than do larger ones. A hummingbird weighing 2.8
grams had 940 feathers or 335 feathers per gram; a nighthawk weighing
67.9 grams had 2034 feathers or 29 feathers per gram; while a swan
weighing 6123 grams had 25,216 feathers or 4 feathers per gram of body
weight.
Presumably there are still other relations: Do the birds that live in
the tropics where it is warm have fewer feathers than species of the
same size of arctic climates, as one would expect? Are certain types of
feathers such as those of aquatic birds better insulated than those of
land birds, so that the bird requires fewer of them to keep warm? Does
a dense coat of down reduce the number of feathers needed to keep warm?
Do the loose feathers of ostriches, lacking barbules, necessitate some
adjustment in numbers? The things we've learned point the way to other
questions to be investigated.
LAST YEAR'S BIRDS' NESTS
[Illustration]
The wisdom of our fathers is sometimes embodied in what we call old
saws, to wit, "Many hands make light work," to which the iconoclast
retorts, "Too many cooks spoil the broth." And when we come to the
phrase, "As useless as a last year's bird's nest," we must reply,
"Circumstances alter cases." For many a bird's nest of yesteryear still
has its use; some a biological use to other birds; some to feed and
clothe man.
SUBLEASES The snug, secure cavity that a woodpecker chisels in some
tree trunk for its nest will last for many years, a shelter in which
tree swallows, house wrens, screech owls, bluebirds, or wood mice
may make headquarters and use as a nursery. In the strange forests of
saguaro, a giant cactus of southern Arizona, the nest cavities of the
gila woodpeckers and the gilded flickers in the cactus trunks seem
necessary for the presence of many nesting birds. Without them the
birds would have to go elsewhere for cavities in which to nest. In old
woodpecker nest cavities the elf owl, pigmy owl, screech owl, sparrow
hawk, ash-throated flycatcher, martin, and crested flycatcher commonly
nest, and cactus wrens and even Lucy's warbler may use them. Their use
is not confined to birds alone, for scaly lizards, snakes, rats, and
mice have been found in them. In the Argentine there is a woodhewer
that appears to depend on the domed mud nest of the red oven-bird for
its nesting sites. It takes over a recently vacated or an old nest of
the oven-bird and lines it with grass and feathers for its own use. In
Africa and Madagascar the great domed nest of the hammerkop stork may
find a secondary use in sheltering barn owls.
SANDPIPERS AND EAGLES But it is not only burrows and domed nests that
when deserted by their original occupants are used by other birds. The
solitary sandpiper of our northlands belongs to a group in which nest
building is reduced to a minimum, usually little more than a hollow
in the ground with a few bits of material added. But the solitary
sandpiper, and the green sandpiper of the Old World have broken with
tradition and customarily lay their eggs in the abandoned nest of some
thrush. Our great homed owl is another bird that may use the discarded
nest of a crow or hawk for its eggs and young. And age in the eagle's
nest means little to the eagle. Frances Herrick, the noted chronicler
of the life of the American bald eagle, writes of one nest in the
crotch of a lofty tree that had been in use for thirty-six years. Each
year more material was added until the nest became 12 feet high, 8½
feet across the top, and was estimated to weigh 2 tons.
Man has found, among others, the following two direct uses for two
kinds of birds' nests: one he uses for food; of another he makes
covering for himself.
The swift's nests used for food have been discussed in another chapter,
"Birds' Nests and Their Soup," so here I will only tell of the use of
birds' nests as human covering.
EIDER-DOWN BLANKETS An eider-down has come to mean a comforter, a
sleeping bag, or even a padded jacket. But to an ornithologist eider
down still has its older meaning: the down of an eider duck. It is this
material gathered from the eider ducks' nests which forms the article
of commerce. The eider's nest may contain grass, seaweed, and sticks,
but it is notable for the blanket of down on which the eggs rest, and
with which the female covers the eggs when she leaves them. This down
is plucked from the breast of the female. If it is taken from the nest
she replaces it with more, and it is on this principle that harvesting
of the down is carried out. On islands and islets in the northern part
of the North Atlantic eiders nest in great numbers in dense colonies.
Some of these are jealously guarded by the local inhabitants, who
gather the first blanket of down from the eggs, and later, after the
eggs have hatched, gather the second crop of down with which the female
has replaced the first to guard her eggs against the inclement weather
of those boreal latitudes. Each nest may yield an ounce or so of the
precious down, which is carefully cleaned and sent to market. It is
this material, extremely light, extremely elastic, and one of the best
non-conductors of heat, which finally becomes the important part of
real eider-down comforters, sleeping bags, and padded jackets.
SYMBIOSIS--ANIMALS LIVING IN MIXED HOUSEHOLDS
[Illustration]
Symbiosis, a term from the Greek, is what the biologist uses for the
living together of two dissimilar organisms. In a broad sense it
includes such diverse relations as the lice living on man and rats in
his house, the union of an alga and a fungus to form a lichen, and the
cross-pollination of flowers by hummingbirds.
The story of the burrowing owls of our Western plains living in amity
with prairie dogs and rattlesnakes as one happy family comes to mind
as an example. But "foolish nonsense" is how the noted biographer of
North American birds, A. C. Bent, characterizes such stories. He then
goes on to quote evidence as to what actually happens, and one can see
how the story originated. The prairie dogs, which are really plump,
dumpy, ground squirrels and not dogs at all, dig their burrows close
to each other on the prairie in colonies which have come to be called
prairie-dog towns, or dog towns or simply "towns." Burrowing owls also
take up their residence in these towns, probably because they find
burrows ready made and do not have to dig their own as they are quite
able to do.
MODERATELY PREDATORY The owls may make an occasional meal of a young
prairie dog, and a prairie dog may perhaps dine occasionally on owl
eggs, but on the whole owls and dogs get along on terms of easy
familiarity. Sometimes when alarmed, both may scuttle into the same
burrow for safety, but each has its own burrow. With the rattlesnake
it is different. The rattlesnake may live in burrows in the dog town,
but when it is hungry it eats owl or dog as occasion offers. While
the picture of a happy family of owl, dog, and snake is a myth, the
symbiosis of owl and dog, at least in the same colony, is striking.
In Africa there is a tiny falcon only about eight inches long which is
called a pygmy falcon because of its small size. When Dr. Friedmann was
studying the social weavers in South Africa, birds which nest in large
colonies under a common roof they make in a savanna tree, he found
these falcons occupying nest chambers in thriving weaver colonies.
There was no friction between the weaverbirds and the falcons, and they
were sometimes seen to sit side by side. When Friedmann collected three
of these falcons he found bird remains in their stomachs but they were
not remains of the social weavers. Apparently the falcons were feeding
largely on small birds, but they did not molest the weaverbirds which
had made the nests the falcons were using.
PARROT-DUCK-OPOSSUM MÉNAGE We occasionally find a mallard nesting in a
tree, on an old crow or hawk nest, and there are ducks like the wood
duck and the golden-eye, which usually nest in holes in trees, but a
South American duck called the tree teal habitually nests in a parrot's
nest. The parrots, called monk parakeets, make their nests in compact
colonies in the branches of trees, so close together that they form
a single mass. The tree teal's usual manner of nesting is to lay its
eggs in one of the chambers in this apartment-house colony. At first
the eggs are laid on the rough twig floor of the nest, but as the eggs
increase in number a lining of down, plucked from the breast of the
bird, is added until it may even extend out the entrance of the nest.
Apparently parrot and duck both get along amicably in their pendant
treetop cradles. An opossum sometimes also finds these parrot nests
to its liking, though one wonders if it may not have a meal of young
parrot or duck in mind. But be that as it may, in different chambers
of a single communal nest of these parrots, parrots, a duck, and an
opossum have been found.
On islets off the New Zealand coast lives a rather large-sized lizard
called _Sphenodon_. It's rather well known by name, at least, for it
is one of those relics of a formerly more widespread group which are
called living fossils. It is also noted for its remarkable development
of a pineal eye, the remnant of an important sense organ in ancestral
forms, and formerly an organ some philosophers supposed to be the seat
of the soul. But here we are interested in the fact that petrels swarm
to these same islands to dig their burrows and lay their eggs in them,
and it is in these same burrows that _Sphenodon_ spends its daylight
hours. Apparently the insect-eating _Sphenodon_ and the oceanic-feeding
petrels share the burrows amicably, adding still another example of a
rather long list of dissimilar organisms whose lives are associated.
BIRD APARTMENT HOUSES
[Illustration]
Every now and then in our press appear blasts against crowded living
conditions in our cities, and the tenements where people are crowded
together. Often there is the implication that this type of thing is
unnatural and abnormal. And yet when we look about us in the bird world
we see that gregariousness is a common trait. We have only to remember
the great flocks of starlings and blackbirds in the autumn, or the
massed flights of water fowl. Not only in traveling and in feeding, but
also at nesting time birds may gather together, and some birds nest in
such close association that the term "apartment houses" or "tenement"
is really applicable.
The martins' house on our lawn with perhaps dozens of closely spaced
rooms (some houses have as many as two hundred rooms) is a case in
point. The neat martin house, made of boards, is a man-made thing,
but even before the white man came to this continent, and before the
Choctaw Indians hung up groups of hollow gourds for the martin colonies
to use, the martins nested in colonies. Even in recent years certain
colonies we might consider unprogressive have been reported as using
such diverse nesting situations as among the boulders of a lake shore
in Minnesota, and the closely spaced woodpecker holes which riddled
a dead pine in Florida. And probably it was always thus. The martins
liked company at nesting.
CLIFF DWELLERS, TOO Perhaps it would not be proper to consider a colony
of bank swallows, each with a separate burrow in the same small cut
bank and roofed with the same few square yards of turf of mother earth,
as a real apartment house of cliff dwellers. But the term has been used
in connection with a West Indian woodpecker, where a dozen pairs were
nesting in a single dead tree, and "the trunk was a veritable apartment
house." A similar situation exists with the naked-faced barbet of West
Africa. This bird too makes a hole in a dead tree for its nest, like a
woodpecker, and colonies of thirty to fifty birds may be found nesting
in a single dead tree, while other dead trees nearby, apparently
equally suitable, are untenanted. Colonies of hundreds of nests of
cliff swallows, the nests touching and overlapping, may be under the
eaves of a single barn, or as they used to be and some still are, on
the sheltered side of a cliff. But as these birds had nothing to do
with the making of the roof, perhaps these too do not deserve to be
rated as apartment houses.
In southern South America there is a monk parakeet that makes a real
tenement. It nests colonially in treetops, and the nests of sticks are
placed so close together that they merge and form a single mass, up to
nine feet across, in which each parakeet has its own nest. Similar to
this is the palm chat. This West Indian bird is small and thrush-sized,
dull in color, brownish with a streaked breast, nothing remarkable to
look at, but it carries amazingly large sticks, little thinner than a
lead pencil and as much as two feet and more long up to the top of a
palm tree, and there it makes its bulky community nest.
BUILD NESTS CO-OPERATIVELY These stick nests, which may be four feet
and more across, are conspicuous and regular features of the landscape
in Hispaniola. The colony consists of four to eight pairs of birds,
and each has its own apartment in the bulky structure, and its own
passageway to the outside. But in the parts of the community nests that
hold the individual nests together and cover them there are roughly
defined passages running through the interlacing twigs of the top of
the nest so that the birds can creep about under cover. Apparently some
of the work is carried on in common, for as many as half a dozen birds
may be working close together, pulling and twisting twigs more firmly
into place.
The social weaver is the most advanced apartment builder. It, like the
palm chat, has little of distinction in its appearance, being mostly
dull brownish with a black face. But in its home country, the savannas
of Rhodesia in southeastern Africa, its huge community nests in the
savanna trees may be seen from afar. The largest Friedmann saw when he
was studying the bird there was about 25 feet by 15 feet, by 5 feet
high, and contained about 95 nests. And this might have been still
bigger, for part of it had broken the branch on which it rested and
fallen to the ground. Sir Andrew Smith, the early ornithologist of
South Africa, has written that when these birds start a colony they
first of all make a roof of coarse grass. The group to which the social
weaver belongs gets its name from the remarkable ability some of them
have of weaving their nesting materials. But the social weaver neither
plaits nor weaves its roof. It puts the roof together in the form of a
well-made hayrick with a fairly definite thatching arrangement so that
the water runs off. This is a community effort. Under this roof each
individual pair makes its own separate nest. These apartment houses are
used year after year, but last year's chambers are not used, new ones
being made under the roof each year, and so it grows bigger and bigger
until the weight of the mass may break the branches and cause a part or
the whole to fall to the ground.
BIRD HELPERS AT NESTING TIME
[Illustration]
In many a well-run American home the children have definite
responsibilities, the older children may help look after the younger,
and even grown-up relatives may stay as part of the family group. As in
so many cases there may be found parallels to this in the bird world.
The ani, the curious tropical American cuckoo that makes communal
nests, is gregarious and the young of the first brood become part of
the parent flock. Two more broods may be raised during one season
in Cuba, and the young of the earlier brood may feed their younger
brothers and sisters of the later brood. The same has been recorded
for many other species in the wild: in eastern bluebirds, mountain
bluebirds, wheatears, long-tailed titmice, barn swallows, coots, rails,
and gallinules young have been recorded as feeding still younger birds.
In captivity this habit has been seen a number of times. Young birds
hardly able to feed themselves may help feed still younger individuals
of the same or other species, and a nestling crowned hornbill has been
seen to offer food to its nestmates. This tendency to feed nestmates
evidently appears very early in the life of the bird, as Dr. C. O.
Whitman, who worked intensively with pigeons at the University of
Chicago, recorded a hybrid dove only twelve days old that fed its
nestmate.
FIVE JAYS AT A NEST It was rather generally known that occasionally
more than the two parent birds attended a nest, but until 1935, when
Alexander Skutch, the authority on the biology of Central American
birds, published his paper "Helpers at the Nest," few of us realized
how widespread this was. Since most birds of a species are difficult to
identify individually, one must actually see the extra, unmated helpers
at the nest along with the parents to be sure they are there. In the
brown jays of Central America that Skutch studied closely the colors of
the soft parts, bill, feet, and eye rings were variable and he was able
to recognize many individual birds. At five nests he watched he found
at least one helper at each nest, and at one there were five helpers,
all bringing food. Sometimes, if between an incoming, food-laden bird
and the young, they would take the food and pass it on to the nestling.
At one nest the unmated helper was more zealous in guarding the nest
than were the rightful parents. Sometimes, perhaps, these helpers were
unmated young of the parents' previous year's brood, but this could
hardly have been the case where there were five helpers, for the brown
jay ordinarily raises no more than three young a year. A black-eared
bush tit of Central America seems to have a great preponderance of
males and at one nest in addition to the parents there were three other
males bringing food to the young.
MATERNAL PENGUINS Perhaps the most striking example among birds is
the emperor penguin. These birds breed in the dark and cold of the
antarctic winter, on the edge of the ice shelf. The single egg is
carried on the feet of the brooding bird; indeed one wonders what other
adaptation for holding the egg would be possible in this land of ice,
snow, and water. Only a few of the adults in each colony lay eggs any
year, perhaps one in five, or one in twelve. But all the adults in
the colony have the urge to incubate and brood. Thus many old birds,
rather than merely the two parents, may take turns caring for each egg
or chick, leaving the rest ample time to feed. So strong is the urge
to brood that struggles may take place over a chick and it may be very
roughly handled. Indeed the chicks may so resent this that they may
creep away into ice crevices and freeze to death. Another strange turn
this behavior may take is that frozen eggs, dead chicks, and even bumps
of ice of suitable size are carried on the feet and covered with the
birds' feathers by their "would-be fathers and mothers."
A NAME FOR A BOAT
[Illustration]
A request for the name of a sea bird, a name to be used for a boat,
came to me at my desk in the museum one day. My memory was quickly
exhausted with sea gull, sea swallow, and albatross. But I keep within
reach the handy guide, _Birds of the Ocean_, by W. B. Alexander. In
the index I found twenty pages of names, two columns to a page. They
started with _aalge, Uria_, and went on down through the alphabet to
_yelkouan, Puffinus_, and to _zimmermanni, Sterna_.
EUPHONY NEEDED A name should be short, pleasant-sounding, and easy
to remember and to say, so obviously such words as _Macronectes_,
_Brachyramphus_, _Aptenodytes_, and _Coprotheres_ are ruled out among
the scientific names. But further, when choosing a name for a boat
from among those of water birds, one should consider the kind of a
boat. There should be some appropriateness; some points of resemblance
between the boat and the bird, or between the boat owner and the bird.
Albatross seems right for a seagoing sailing ship, sailing to southern
oceans; tern (or sea swallow) appropriate for light, dainty coastal
sailing craft; puffin or auk or murre for power craft, for these birds
spend most of their time stolidly on the water and when they fly have a
direct buzzing flight. Loon and dabchick would do well for fresh-water
boats. But one objection to both them and the various auks for a name
is that these birds spend much time swimming underwater. They might
better give their names to submarines. The big, stocky sea ducks,
called scoters and eiders might suit some stout craft that ply to
arctic waters.
SCIENTIFIC NAMES AVAILABLE I reviewed the host of other names.
Scientific names need not be ignored either. What is nicer than
_Gygis_, the name of the white, fairy, or love tern of the South Seas
for a small summer sail boat? Then going farther afield into austral
waters for far traveling craft there's _Diomedea_, the name of the
albatross, and _Daption_, the medium-sized petrel that also is called
pintado for the same reason a white-splashed horse is called a pinto,
and _Prion_, the tiny whalebirds of the antarctic whose blue-gray back
is near the ideal ocean-camouflage color. _Larus_, a good honest name
without frills, belonging to the gulls that haunt our harbors, coasts,
and lakes, would do for a plain, everyday sort of boat. Kittiwake is
another gull that spends more time at sea. Gannets are boldly black and
white, strong-flying birds of the North Atlantic, and one could use
that, or its scientific equivalent, _Moris_, for a boat.
Penguin and pelican I'm doubtful about; I can't imagine a boat for
either. Skua or jaeger would, of course, be a lovely symbol for a
pirate vessel, as would frigate bird; both are birds that practice
the stand-and-deliver method of getting food from weaker fisherfolk.
The petrels called shearwaters are among the hardiest seagoing birds,
but the name has little association for most people beyond wondering
if they feed around breakwaters. Petrel itself isn't a bad name,
though one might think of the storm petrels, which are also called
Mother Carey's chickens, and have been considered the souls of drowned
sailors, though their name perhaps refers to Peter, and his attempt to
walk on the water, as these birds are continually trying to do.
Phalaropes are snipes of sorts that have taken up a periodic seagoing
habit, and their name might often be appropriate. Even their habit of
spinning quickly about as they sit on the water might still agree. A
Chicago man named his Chris-Craft _Sandpiper_, after, as he said, the
bird that goes hopping along the beach before the waves.
_Sula_ is a good sort of a word, and the name of birds that are strong,
swift fliers of the tropics. But in English they're usually called
booby, which is an English word meaning simpleton (which name the birds
got from stupidly perching on ships). _Alle_ for the little auk or
dovekie would do for a tiny boat in northern waters, and I knew of one
boat called the _Alca_, after the razor-billed auk, while _Cepphus_,
the name of the black guillemots, is equally good, as is both _Lunda_
and its equivalent puffin.
Some names have a stark simplicity that would attract few, like shag,
used for the cormorant, and muttonbird for a petrel. The cahow people
might shy from because for many years we were not sure whether this
West Indian petrel was extinct or not.
Myself, there are two names I rather like and I've been saving for the
last: for a small sailboat I'd say the _Wideawake_, as the sooty tern
is called in its tropical home, and the other, for a larger seagoing
boat, is the _Mollymawk_, a sailor's name for the albatross.
WEAVERS AND TAILORS IN THE BIRD WORLD
[Illustration]
One can imagine the consternation in trade-union circles when it
becomes known that there are, among birds, those who weave and those
who sew. Their products are entirely for home consumption and there
are no minimum wage, no maximum hours, or any fair-trade or quality
agreements. None of the Audubon societies have even touched on the
matter.
WEAVING The sewing and the weaving is done entirely in the construction
of nests. To take up the weavers first, we can point to the Baltimore
oriole, which makes a sac-shaped, pendant nest, often hung from the
trailing tips of elm branches. The walls of this sac are formed of
fibers pushed and pulled back and forth with the birds' bills in a
seeming haphazard way so that a roughly woven or stitched fabric
results. But the finest weavers belong to that group of birds known
as weaverbirds. One might expect that to be an expert weaver a bird
would have to have a slender bill. But no, their bills are short,
stout, clumsy-looking, and sparrowlike. And yet these are the birds
that weave elaborate pendant nests of fibers and straws. The finest
are in shape like an inverted retort, with the nest proper in an oval
chamber, fastened to a branch by a special strand of fibers, and with
a tube or funnel for an entrance. The walls of these fine weaverbirds'
nests are amazingly strongly and neatly woven. In captivity one of the
weaverbirds, the red-billed weaver, was studied at its nest building
and it was found that the strong, intricate, and beautiful weaving of
this species actually included knots of several sorts.
TAILORING The tailoring is done by birds of quite another group. They
are Old World warblers of several sorts, some in southern Asia and
some in Africa. The tailoring consists of sewing the edges of leaves
together to form a place for their tiny nests. The Indian tailorbird is
perhaps the best known. When these tiny olive-green and gray birds set
about nest building the female punctures the margins of the leaves with
her bill. Then she brings cobwebs and pushes them through the punctures
in the edges of the leaves, and winds them around, and draws the edges
of the leaves together. Strands of cotton are used too for this.
Sometimes a single leaf is used; its two edges being drawn together
to form a funnel. Sometimes a number of leaves are joined. Sometimes
it is claimed knots are used, but this seems not to be the case. What
are mistaken for knots seem made in this way: The cotton used is soft
and frays easily, so that the part of it forced through a tiny aperture
issues as a fluffy knob, which looks like a knot. "The bird makes no
knots; she merely forces a portion of the cotton strand through a
puncture," and the edges of the puncture catch and hold it, according
to Casey Wood, who studied the birds in India. The lining of the nest
is of soft material and this the bird anchors by making a puncture in
the leaf, grasping a strand of this material, and pulling it out; the
cotton outside then expands into a minute button which helps hold the
nest and contents in place as though riveted. One nest is recorded as
having been so riveted in seventy-five places.
The camouflage of the tailorbirds' nests is very good; it is usually
built in thick foliage, the leaves are little deranged, the punctures
do not cause the leaf to die; and the leaves being the same as the
others, there is little for the eye to pick up as indicating a bird's
nest.
SOCIAL PARASITES AMONG BIRDS
[Illustration]
The mother who would leave her infant on a stranger's doorstep, to be
brought up an orphan, not even knowing its own parents, is a despicable
character in human society. But when we leave the man-made society we
must leave man-made rules of behavior and man-made prejudices behind.
Morals are human. The rest of the animal world is not immoral, it is
amoral. It cannot afford criteria beyond survival and reproduction. So
while we call certain birds "social parasites," we attach no stigma to
them. They represent several groups: the cowbirds, the weavers, the
cuckoos, the honey-guides, and the ducks.
Carelessness in egg laying is common even in birds that ordinarily
lay their eggs in their own nest and care for them themselves, as for
instance the robins' eggs that you may find on your lawn (which of
course are wasted; addling and rotting). Perhaps the fate of the eggs
of pheasants and ruffed grouse which are found in the same nest may
be more happy. Ducks usually make their own nests, but many species
occasionally lay eggs in the nest of another species, and one South
American duck no longer makes any nest of its own, but is a social
parasite, not only on other kinds of ducks, but also on coots and some
other birds.
The small, well-marked family of honey-guides of Africa, notable in
other ways, also is remarkable for being social parasites. Their
favorite host species, chosen to look after the eggs and young, are
their close relatives, the barbets (which themselves are most closely
related to our woodpeckers).
The nesting of certain African weaverbirds was long a puzzle to
ornithologists until it was found they too were social parasites, on
other weaverbirds.
VARIED NESTING HABITS The cowbirds, of several species in North and
South America, belong to a family notable for the variation in its
nesting habits. Their nests vary from the elaborate purse-shaped
structures of the oropendola and orioles to the dome-shaped nest on the
ground of the meadow lark, the simple cup of the bobolink and redwing;
the cowbird makes none. The cowbird lays its eggs in the nests of a
wide variety of other species to be cared for by them. Here those who
discuss the relative importance of heredity versus environment can
profit by considering these social parasites. The young cowbird,
hatched and brought up by, say, a yellow warbler, remains a cowbird.
As soon as it no longer needs its foster parents' care it flocks with
other cowbirds, with all their mannerisms and characteristics, and next
season it mates with another cowbird. There is nothing left of its
early environment.
The cuckoos of the New World and some of those of the Old make their
own nests in normal avian fashion. But a number of Old World species
are social parasites, and their behavior has long been a subject of
study and discussion. Specializations indicate that here perhaps we
have the highest stages of social parasitism. Whereas the cowbird may
grow up with nestmates that are the young of the foster parent, unless
perchance it crowds them out or starves them if it is larger, the young
cuckoo gets the rightful occupants of the nest on its back and throws
them out of the nest to perish.
EGGS LOOK ALIKE Another refinement in social parasitism by the European
cuckoo is that apparently certain individuals, and apparently certain
strains, lay their eggs only in the nests of certain host species.
And these cuckoos' eggs resemble those of the particular species in
whose nest the cuckoos' eggs are laid. For example, if certain cuckoos
lay their eggs only in the nests of meadow pipits these cuckoos' eggs
would resemble those of meadow pipits, while another group of cuckoos
specializing in hedge-sparrows would have eggs resembling those of
hedge-sparrows. Another oriental cuckoo has a color adaptation in
the young. In southern Asia these cuckoos parasitize crows, and the
nestling cuckoos have black feathers like the young crows; in the
Australian area where the same species of cuckoo occurs it parasitizes
grayish-brown honey eaters and the young are brown, more like the
rightful nestlings. Both these resemblances apparently reduce the
chances of the cuckoos' offspring being rejected by the foster parents.
FISH EATS BIRD!
[Illustration]
It has become commonplace to hear about birds eating fish. The
government gets out reports on the relation of fish-eating birds to
fish abundance. The cries of commercial fisheries have caused inquiries
to be instituted into the food of cormorants that were supposed to be
eating the fish before they grew up enough for us to eat. The scarcity
of salmon in some of our Northeastern streams has caused the allocation
of biologists to study the predation of kingfisher and merganser on
salmon fry and fingerlings.
But fish get some of their own back by eating birds. It's not as spot
news as the "man bites dog" angle, but it's certainly less widely
known.
To one who has fished for large-mouth black bass among the cypress
trees and the bonnets of water hyacinth, and seen the bass strike
savagely at surface lures as soon as they hit the surface, it comes as
no surprise to find they strike at, and catch, such birds as Maryland
yellow-throats that flutter across close to the surface of the water.
Young ducks, too, are good game to the large-mouth, and probably many
a young duck finds its way into the maw of a bass. On a pond where
bass had taken many young ducks I heard a story of a fisherman who
made a floating model of a mother duck, powered it with a propeller,
and attached to it by lines of various lengths several floating models
of downy ducklings. In each duckling was concealed a hook. The whole
flotilla was set afloat, and drifted across the pond. Mother steamed
ahead, with young following. Soon the bass, used to a duck diet, began
to grab the ducklings. When the model was retrieved several large bass
were taken.
In Northern waters, where Northern pike, or jackfish, as they're called
in the North, abound in duck-nesting waters, pike are accused of eating
enough ducklings to affect the survival of the broods. Many a marshland
traveler has reported young ducks and young grebes diving, to be seen
no more. He's blamed the pike. Sometimes perhaps the young bird has
simply come up unobserved. But enough pike's stomachs have proved
to have young ducks in them to demonstrate pike do eat ducklings.
Strangely, in some areas, pike eat many ducklings; in others they do
not eat them. But it's not alone young birds or small birds that get
eaten by fish.
A twenty-four-inch bass is recorded as having been caught while it
still had the legs of a full-grown coot projecting from its mouth. From
beak to tip of its outstretched legs the coot measured seventeen inches
and it weighed one and one quarter pounds.
Angler fish weighing between forty and fifty pounds have been found
to have eaten birds. One had the band from a Manx shearwater in its
stomach, and another had an adult American merganser. In tropical and
subtropical seas the examination of birds seemed to indicate they had
been attacked by some fish and seized by the feet, but were able to
escape, and a white-winged black tern off Corsica has been seen to
disappear under the water, presumably dragged under by a fish.
CROWS ARE SMARTER THAN "WISE" OWLS
[Illustration]
The owl has always been considered the symbol of wisdom. The old saying
has it that "fine feathers don't make fine birds," but I'm afraid that
the owl has taken in people with its appearance. The owl's reputation
for wisdom seems to be based on a staid, impressive appearance combined
with an inarticulate disposition. Though owls do at times make a great
deal of noise, hooting, shrieking, and whistling, much of the time the
owl sits quietly looking wise and saying nothing. But owls don't seem
to have much behind the front they put up. People who have studied
them find the young are very slow to learn to feed themselves, and one
saw-whet owl that was kept captive refused to eat liver put into its
cage, apparently not recognizing the meat as food. But when the liver
was stuffed into an empty mouse skin the owl at once ate it. One might
conclude that the owl was the original "stuffed shirt."
The crows and their relative, the jays, are the birds that are really
intelligent. They are active and usually have little trouble getting
enough to eat. They have an abounding curiosity that leads them to
spend their time investigating things and getting new experiences. And
they seem to profit by these experiences, too.
The following is how three ravens co-operated in getting a bone from a
dog, as written by B. J. Bretherton:
"He was espied by a raven who flew down and tried to scare the dog by
loud cawing, in which he was shortly afterwards assisted by another,
both birds sidling up to the dogs head until they were barely out of
his reach. Just at this time a third raven appeared on the scene and
surveyed the situation from an adjacent fence, but soon flew down
behind the dog and advanced until within reach of his tail, which he
seized so roughly that the dog turned for an instant to snap at him,
and at the same moment the bone was snatched away by one of the ravens
at his head."
CROWS LEARN FROM OTHERS Crows have been recorded as profiting by
the experience of one of their numbers. In Washington, when almonds
were ripening in the almond orchards and crows were swarming there
threatening to destroy the nut crop, an estimated 30,000 crows were
involved and the destruction of an $800 crop was complete in two days.
Various methods of control were tried unsuccessfully. Finally some
almonds were slit open, poisoned, and scattered about in the orchards.
Very few crows were actually poisoned, not exceeding 1 per cent of the
flock. The first reaction of the crows when one of their number was
poisoned was one of extreme panic. There was tumultuous clamoring and
confusion. Then the flock abandoned the attempts to feed on almonds and
left the area completely. Here we have a case of superior intelligence,
birds profiting by the sight of a few of their numbers being poisoned
fleeing the area and so escaping being poisoned themselves.
TAME WILD BIRDS
[Illustration]
We think of wild birds as being shy creatures by nature. For those
of us who have kept a feeding station for birds in the winter so as
to have the pleasure of association with the chickadee, nuthatches,
woodpeckers, and other visitors, one of the most attractive things is
that the wild birds become tame. Through association with persons they
gradually learn that human beings are not to be feared. The high point
of many a bird lover's experience is when a chickadee becomes so tame
that it will perch on his body and without fear will feed from his hand.
It seems to be true that birds in wilderness areas are wilder and more
shy of men than those living about dwellings where they are protected.
This is notably true of the robin. In villages they hop around on the
ground unmindful of the near presence of humans. How different they are
in the wilderness, where the robins fly away apparently in great fear,
while the human intruder is still far distant.
It comes as a considerable surprise to find that here and there over
the world there are instances of birds with so little fear of humans
that they come and perch on them.
PERCHING ON PEOPLE In the Galápagos Islands, where the general
fearlessness of birds is famous, one of these cases is recorded. David
Lack, who was studying the biology of the Galápagos Islands' birds,
found when walking through the woods on Indefatigable Island that a
flycatcher would sometimes try to settle on his head. Lack stood still
and found the bird's object was to pull out some of his hair. The bird,
having failed to detach any of the hair of his head, tried, apparently
with no better success, to pull out hair from his eyebrows and then
from his chest. This was at the height of the breeding season and
apparently the bird was trying to get nesting material. This seemed
to be a usual type of behavior there, and Lack correlated it with the
general tameness of the birds on the islands.
There is a honey eater in Australia that includes in its pattern of
behavior perching on people's heads and shoulders and attempting to
pull out hair for use in its nest. A. H. Chisholm writes of going
to certain places and taking companions with him for the sake of
experiencing this, and the practice is so common with the species
that Australians refer to this honey eater as "the hair dresser."
In this case it is not tameness alone. The white-eared honey eater,
which indulges in this practice, is no more tame most of the time
than any of the other small local birds that live in that part of
Australia. Only at nesting time does it attempt to light on persons.
Chisholm correlates this hair-plucking trait with other habits of the
honey eater: he speaks of its gathering hair from such animals as rock
wallabies and gathering bristles from farmyard pigs and goats.
Our familiar phoebe has been recorded as perching on deer hunters
in the fall and using them as a vantage point from which to conduct
its hunting. This was in North Carolina, and the weather being warm,
mosquitoes were notably in evidence. The bird showed no sign of fear or
nervousness, but perched on the hunter's gun, on top of his head, and
various parts of his body, and then flew out and picked up mosquitoes.
As the hunter's face seemed to be attracting more mosquitoes the phoebe
directed his attentions there. In picking mosquitoes off his face the
sharp points of the bird's bill were noticeably felt at every capture
and the irritation caused by a succession of these pricks caused the
hunter to decide that he could take care of the mosquito situation
better without the help of the phoebe. As H. H. Brimley, the hunter,
put it "... my face was beginning to feel somewhat inflamed from the
frequent pecks to which it had been subjected so I called it a day and
told the phoebe to stop pestering me." This took place in a wild part
of North Carolina and Brimley suggested that the phoebe's abnormal lack
of fear was caused by its having never seen a human being before.
BIRDS AS PILFERERS
[Illustration]
Pilfering, or petty theft, is one of the less desirable but very human
attributes of our race. But it's also pretty widespread in the animal
kingdom. Theft as the usual thing is practiced by only a few birds.
But when it's a case of petty theft, happening now and then, it is
common enough in the bird world. It's not restricted to any group of
birds, but may crop up almost anywhere. There's no threat or fight
about it usually. The bird, which gets its food by means of the acuity
of its vision and the quick co-ordination of its movements with the
recognition of its food, sees the food in another bird's possession and
just goes up and takes it. Sometimes the food is taken from a larger
and stronger bird, an achievement accomplished by audacity, agility,
and quickness. A sparrow hawk, that inoffensive little rufous-red
falcon that spends most of its time catching grasshoppers, was sitting
on a telephone wire holding a small mammal it had caught, apparently
about to devour it, when a loggerhead shrike sitting nearby flew
straight to the hawk, seized its prey, and made off, leaving the hawk
sitting there, apparently dumfounded by the audacity and success of the
attack. A case in which the pilfering caused a mild fuss involved an
English kingfisher and a dipper. The kingfisher lit above a pool where
a dipper was feeding, obtaining food in the pool and bringing it ashore
to eat it. When the dipper next came ashore the kingfisher flew down,
there was a momentary scuffle, and the dipper departed, leaving its
food to the kingfisher, who promptly ate it. Despite this occurrence
the dipper allowed itself to lose its prey again before it left, and
the kingfisher presumably had to resume fishing for itself.
THEFT NOT RESENTED It is sometimes surprising that this pilfering,
when it occurs over and over again, is not actively resented,
particularly when the pilferer is a smaller bird. Some of the thrushes
are especially docile when they're victimized. Sometimes when American
robins are feeding on the ground, house sparrows hop along with them,
and when the robin finds a worm the sparrow hops up quietly and boldly
takes the worm from the robin with scarcely a protest from the victim.
One robin is reported to have been robbed six times, of six worms, one
right after the other by a small flock of sparrows while the robin
continued to hunt for worms.
The starling, an aggressive Old World species introduced and very
successful here, also victimizes the American robin. In one case a
starling made four successful raids in five minutes, the robin not
attempting to fight or defend its food, but simply moving off a little
way and continuing to hunt for worms while the starling waited nearby.
This is not a new trait of the starling, for in its Old World home, in
Britain, it has been seen to victimize blackbirds and song thrushes
(relatives of our robin). This happened when a blackbird pulled up
a worm, a starling flew to the spot, and the blackbird moved away,
leaving the worm to the starling. This method of obtaining worms was
sometimes used by all the starlings on a lawn where both species were
feeding, much to the hindrance in the feeding of both blackbirds and
song thrushes.
Gulls have been recorded as snatching fish from mergansers that had
caught fish by underwater dives and brought them to the surface to eat.
Gulls also follow pelicans, and just after the pelican has completed
its plunge and before it can swallow the fish protruding from its bill,
a gull may flutter in, alight on the water or even on the pelican's
head, and seize the fish. The pelican does not attempt to do anything
about it, but accepts the pilfering with stoic calm.
Grackles victimizing ibises seems perhaps the strangest of the whole
series of reports. The ibis often attempts to elude the grackles but
without success. About Lake Okeechobee, Florida, where ibis are common,
they feed largely on crayfish, which they secure by probing the holes
made by these creatures. Grackles swarm there, and, on occasion, no
sooner does an ibis seize a crayfish than one to four grackles try
to secure it. The ibis may take flight and attempt to escape with its
prey, but one of the grackles usually gets the crayfish away from it.
Possibly some of these birds are on their way to becoming habitual
pilferers, in which such social parasitism is a fixed mode of life.
With evolution, if this thieving benefits the species that snatch
the food, it may become a usual habit. For habits, like structures,
are subject to variations, to selection, and thus to change and
elaboration.
HIBERNATION IN BIRDS
[Illustration]
Not until 1948 did the scientific world have satisfactory evidence that
any bird hibernated. True, it was an established fact that sometimes in
cold weather some birds, notably swifts and hummingbirds, might become
torpid for a short time, but this was not hibernation.
The early literature, of more than a century ago, contained many
accounts, some claiming to be firsthand, of birds hibernating. Swallows
in particular were reported as seen to submerge in ponds in the autumn.
Numbers of them were said to have been found hanging to submerged
willow branches apparently sleeping the winter away. When ponds were
drained in winter, sometimes swallows were said to have been found
buried in the mud, revived, and upon occasion kept alive indoors
until the spring. Sometimes slime-covered swallows, evidently just
out of hibernation, were reported found in the spring. Swallows were
the most commonly recorded, but other species, too, were mentioned as
hibernating, such as the cuckoo that shed its feathers and crept into a
crevice to sleep away the winter.
Such accounts gradually disappeared from the literature. We can accept
none of them. The old records of underwater and also the featherless
hibernation of birds must be discarded. The occasional torpidity, in
cold weather, of swallows, swifts, and hummingbirds is another matter,
and appears to be of sporadic though not common occurrence.
FROGS MISTAKEN FOR BIRDS It is interesting to speculate as to how
the old "firsthand" accounts originated. They had certain basis of
fact. The first was that swallows were seen flying about in summer.
They disappeared in winter. Aristotle claimed they hibernated, in a
featherless condition, so there was nothing unusual in seeing them
that way. Observation was less critical, and it is probable that frogs
from the mud of ponds were mistaken for naked swallows, and perhaps
bats, which do hibernate, taken from caves or hollow trees, were also
mistaken for swallows.
AN AUTHENTIC RECORD In 1948, and again in 1949, Edmund C. Jaeger, of
California, published accounts of a poor-will he found hibernating.
This was the first acceptable evidence that such a thing occurs. In a
little cavity in the wall of a canyon in the Chuckawalla Mountains of
the Colorado desert in California, Jaeger found a poor-will in a state
of profound torpidity in December, 1946. He could pick out the bird in
his hand, examine it and put it back in the little cavity it occupied
without eliciting more than a slight movement of its eyelids. On a
later occasion handling it revived it somewhat.
The next winter Jaeger found a poor-will, perhaps the same bird,
hibernating in the same niche. Over a period of eighty days, from
November 26, 1947, to February 14, 1948, he visited it periodically,
examined it, and took its temperature. The body temperature was low,
64°-68° F., compared with more than 100° F. of an active bird; with
a medical stethoscope he could detect no heartbeat, and a cold metal
mirror held directly in front of its nostrils collected no moisture
from its breathing. The body processes were evidently very low. The
bird was banded for identification, and in the third winter the same
bird wearing the same band was found to have returned to hibernate
again in the same rock niche. But on subsequent visits it was
missing--perhaps having lived out its allotted span, perhaps the prey
of some predator.
SNAKESKINS IN BIRDS' NESTS
[Illustration]
There are occasionally discovered behavior patterns of birds that are
so unusual as to make one stop and wonder. They are unusual for birds
generally, but in a species here and there they are the regular thing.
Such is the placing of a shed snakeskin in their nests by some birds.
A bird like the English sparrow, or the road runner, which uses a
variety of material coarse or fine, would be expected to use shed
snakeskins occasionally, as it came across them. But there are a number
of species that seem to use snakeskins regularly in their nests.
It would seem that the birds deliberately sought out the skins for
this purpose, as though they were as much a part of the nest as the
mud in the bottom of a robin's nest or the fresh green grass heads
ornamenting the entrance to some weaverbirds' nests.
SOME HABITS BAFFLING I have long since given up thinking that every
aspect of a bird's life must serve a useful purpose. Indeed I have
already pointed out some definite maladaptations. But usually every
type of behavior has a logical origin. By considering its occurrence in
various species and against the background of the bird's everyday life
some correlations usually can be found.
The list of birds habitually using snakeskins in their nests is short,
as follows:
1. Great-crested flycatcher--belonging to the New World flycatchers,
breeding in Eastern North America and nesting in holes.
2. Arizona crested flycatcher--a relative of the great-crested variety,
with similar habits.
3. Blue grosbeak--an American member of the sparrow family, making an
open nest in bushes.
4. Black-crested titmouse--a member of the chickadee family, living in
Western North America and nesting in holes.
5. Bank mynah--a starling, living in southern Asia and nesting in holes
in banks.
6. Rifle bird--an Australian bird of paradise, making a cup-shaped nest
in trees.
7. Madagascar bulbul--making a cup-shaped nest in trees.
LIKE A DECORATION Twenty or more other species of birds have been
recorded as using snakeskins more or less commonly, or occasionally
perhaps on the basis of availability or of chance. But with the above
they're an essential part of the nest. In some of the species the
snakeskins are arranged as a rim around the edge of the nest almost as
a decoration; sometimes the snakeskins may make up most of the nest.
Now as to possible correlations. The species are not closely related.
Except for the two flycatchers the other five represent five different
families. The distribution over the world is wide, too: America, Asia,
Madagascar, Australia. Various explanations for the behavior have
been advanced. It has been suggested that it's correlated with hole
nesting, but three of the seven do not nest in holes. The most common
theory is that it's to frighten away possible predators by making them
think there is a snake in the nest. However, this is not very likely,
and, too, one wonders why the birds that use the snakeskins are not
frightened themselves. Indeed, one writer, surely not seriously, has
suggested that the fright in early life of crested flycatchers at
finding a snakeskin in the nest accounts for the upstanding crest in
this species!
"BURGLAR ALARM" THEORY Another suggestion is that the snakeskin, by
the rustling noise it makes when touched, acts as an alarm bell or
a burglar alarm to warn the rightful occupants of the nest when an
intruder approaches. This also seems a rather weak explanation.
We are left, then, with the fact that this curious habit has been
developed in a few birds, not closely related, that live in various
parts of the world and that have very different habits. It is usual
with them. A number of others occasionally have this habit.
My first clue as to the proper background against which to solve this
habit came when, unpacking a bird collection made in Borneo by curator
of anatomy D. Dwight Davis, I took out a bulbul's nest. In its outer
edge were flat, weathered leaves that resembled snakeskins. Later, when
we received a bird collection from Dr. D. S. Rabor of the Philippines
there was a nest of another species of bulbul and this too had flat,
dead, weathered leaves in it that looked like snakeskin. When I was
in Madagascar, in 1929-31, I had found three nests of the Madagascar
bulbul with a snakeskin used in each. Here was a clue. I decided to
investigate the nests of the other species of bulbuls of southern
Asia and Africa where the family is represented by many species. By
considering the snakeskin-using species against the background of the
nesting of the other species some correlation might appear.
BOOKWORK This became a library problem at once. I had to look up
the earlier reviews of the problem in the ornithological journals,
_The Auk_ and the _Ornithologische Monatsberichte_, then in Strong's
_Bibliography of Birds_, to make sure that no important papers were
missing from my own subject file. Stuart Baker's _Fauna of British
India, Birds_ had a large part of one volume devoted to bulbuls, and
gave excellent summaries of the nidification of each species occurring
there. Bannerman's _Birds of Tropical West Africa_ covered the western
part of that continent, and Jackson's and Sclater's _Birds of Kenya
Colony_ did the same for the eastern part. For collateral material I
looked in Mathews' _Birds of Australia_, Volume 12, Forbush's _Birds
of Massachusetts_, and Mrs. F. M. Bailey's _Birds of New Mexico_, and a
dozen minor publications.
But it was worth it.
Perhaps my earlier thinking was dominated by the thought that the shed
snakeskins had been parts of animals toward which many birds show an
antipathy. But it's extremely probable a bird does not recognize the
snakeskin as such. Rather to it the shed snakeskin is a strip of thin,
flexible material. Obviously it would be used, by chance, by many bird
species, such as the house wren, which, in addition to using such
natural materials as twigs, grass, and hair, has been recorded as using
lead pencils, paper, nails, safety pins, and snakeskins in its nest.
As to the regular users of snakeskin, the snakeskin-using Madagascar
bulbul did fit into a pattern. Bulbuls in general make characteristic
simple cup nests. Some species use almost any available material. But
quite a few species had specific choices of materials: one species'
nest had tendrils of vines in its base; another a lining of grass heads
of a certain color; another pine needles; another red dead leaves; and
the Madagascar bulbul snakeskins.
A SOLUTION There seems to be a tendency for many species to make
distinctive nests. They often accomplish this by a choice of material
used by few or no other species. What more natural than that one
species, being in a country where snakes are common, should hit on shed
snakeskins!
To show that the choice of snakeskin as nesting material is an
expression of a tendency for each species of bird to make a different
kind of nest may not be much of an answer. But it is to an extent.
No longer do we say, "Why are certain birds' nests characterized by
snakeskins?" Rather we have the broader, more general question, "Why
does each kind of bird tend to build a nest different from that of
every other kind?" Thus, little by little, we clear away small, vexing
questions and resolve them into larger, more general questions. For
answers to these we sometimes plan extended work involving field
studies, studies of specimens, and books. And sometimes, as we examine
a specimen, read a paper, or unpack a shipment, an answer, or at least
a clue, springs to our mind.
CO-OPERATION BY BIRDS
[Illustration]
The importance of co-operation, contrasted with competition, has
assumed increased importance in discussions of evolution, as it has
in discussions of human social progress. Co-operation in nature is of
various kinds; from the manner in which a forest shelters the squirrel
to the manner in which two or more individuals of one species work
together for a common object. The working together of two birds to rear
a family is so well known an affair that one forgets that it is an
example of co-operation, not only in building the nest and brooding and
feeding the young, but also in defending the nest and the young.
Sometimes more than one species will join in ousting an enemy. For
example, when a cat caught a young robin, recently out of the nest,
the parents, in their frantic effort to make the cat release the bird,
attracted the attention of another robin and a pair of cardinals
nesting nearby in a honeysuckle. All five birds dived at the cat,
screaming and pecking it so vigorously that it released the young robin
and fled.
EAGLES JOIN EFFORTS More spectacular are some of the co-operative
activities of birds in food getting. Bald eagles sometimes feed on
ducks. Frequently two eagles may combine their efforts. The two birds
may work together to force a black duck from the air onto the water,
and when they are trying to catch a diving duck, they much more quickly
exhaust their prey by swooping at it in turn. Bald eagles sometimes
take water birds too large for them to carry, and then they must flap
along dragging their prey on the surface of the water to the nearest
shore. On one occasion an eagle dragging a large cormorant ashore was
joined by two other birds, and all three took turns in dragging it.
When they got it ashore, all three shared it.
Several fish-eating birds co-operate in capturing their prey. "The
merganser is primarily a fishing duck ... very skillful and a voracious
feeder. It pursues underwater and catches successfully the swiftest
fish. Often a party of sheldrakes may be seen fishing together, driving
the panic-stricken fish into the shallows or into some small pool where
they may be more easily caught," according to A. C. Bent.
When a school of fish approached a flock of white pelicans, the birds
suddenly assumed a circular position, surrounding the school. All the
pelicans moved slowly but cautiously toward the center of the circle,
their heads near the surface of the water or partly submerged and their
necks slightly extended. The birds moved in perfect unison, making the
circle progressively smaller, ready to engulf their helpless victims at
the first opportunity. When all the pelicans were close to the fish,
the birds made rapid jabs at the fish and apparently consumed a large
number of them. It appeared that every bird got from one to several
fish.
13,000 BAND TOGETHER Avocets and, to a lesser extent, the black-necked
stilts also band together for co-operative drives on small fry and
aquatic insects. Such drives are made in water of wading depth.
Instead of forming circles the birds present compact spearhead and
wedge formations and sweep the bottom muck with the characteristic
back-and-forth side movements of their long bills. As many as 13,000
avocets have been observed taking part in such co-operative feeding
projects.
Another striking example is furnished by black vultures observed by
E. A. McIlhenny. A three-quarters-grown skunk was wandering across a
field. A vulture alighted near the skunk which immediately stopped
and raised its tail. Other nearby vultures joined the one nearby the
skunk, and when six or eight of them had gathered one suddenly attacked
it. The skunk immediately discharged its defensive scent, but without
effect, for the vultures attacked in a mass and other vultures circling
above joined in until there were probably twenty-five or more around
the skunk. With much flapping and croaking, the vultures pulled it
about until it was dead, and then devoured it.
On another occasion a black vulture came from high in the air to
alight near two full-grown opossums following a narrow cattle trail.
The first vulture was almost at once joined by many others until there
were probably between seventy-five and one hundred black vultures
following the opossums. Suddenly three or four of the vultures attacked
and the others joined in. Quickly both opossums were covered with a
swarm of hissing, flapping birds, and within fifteen minutes there was
nothing left of them but the larger bones and the hides, and these were
stripped of every vestige of flesh.
WATCHDOGS AT THE NEST
[Illustration]
A savage watchdog outside his master's house helps to protect it. If an
intruder comes, the watchdog, if it's the right kind, simply bites him
without preliminaries. There's a parallel to this in the bird world.
Some birds often have their nests close to wasps' or bees' nests, or in
trees inhabited by biting ants. The birds and the ants, wasps, or bees
get along without disturbing each other. But when intruders come along
the insects swarm out, biting or stinging and driving the intruder
away. The insects are protecting their own homes, but one of the
results, the protecting of the birds' homes, is just as satisfactory to
the birds as if they did it on purpose. This building of birds' nests
close to wasps' nests is a common practice with certain sunbirds and
weaverbirds, especially in Africa. It occurs too often to be chance.
The question naturally arises as to how much the birds understand of
it all--do they actually seek out the association? That's difficult to
say, but the facts of the association are still there.
Though some of these associations are evidently fairly common and
chosen deliberately by the birds--and one can easily visualize how the
protection works--field observations as to the natural enemies against
which they are effective, and how effective they are, are largely
lacking. Usually the records are something like those of Van Rossem for
the Giraud's flycatcher in El Salvador, in which he points out that
this bird usually nests in certain mimosa trees armed with numerous
heavy, curved thorns. These thorns are hollowed out and inhabited by
swarms of small but extremely hostile antlike insects, so that the nest
is well protected. However, the effectiveness of ant and bee protection
against human predation can be seen in the following.
Take the case of Mr. M. E. W. North, who arranged a rope to climb to a
fish eagle's nest in East Africa. He had gotten about fifty feet up and
was considering going out on the big limb on which the nest was, when
he noticed a wild bee on his sleeve. Realizing that he was disturbing
a wild-bee hive, and knowing that the sting of these vicious bees can
be dangerous, fatalities having been reported, he came down his rope
at express speed, crashing through projecting branches and brambles.
Reaching the ground, he freed himself from the rope and fled to a safe
distance, considering himself lucky to have received only three stings.
On another occasion, again in East Africa, Mrs. R. E. Moreau attempted
to reach a hawk's nest to measure the eggs, but when she was up in the
tree, savage, biting red ants drove her out.
BIRD GUIDES TO HONEY
[Illustration]
In Africa there are birds which lead men to honey. They are called
honey-guides and their family name, Indicatoridae, has the same idea
incorporated into it. Though there are several species of these small,
dull-colored birds, which are related on the one hand to woodpeckers
and on the other to barbets, it is only one species, the common or
black-throated honey-guide that is well known as a guide to honey.
The traveler in the country may find one of these birds chattering and
flying ahead of him. The natives, who know this bird well and favorably
will tell the traveler to follow; it will lead to a bee tree. The
native, as he follows this guide, gives occasional whistles, as if to
encourage the bird. The bird continues, flying from perch to perch,
ahead, and chattering noisily. Sometimes it may return to see if the
men are following; sometimes it remains chattering on its perch until
the followers catch up. Finally the bird will go no farther. It flies
about aimlessly and allows one to approach closely. This is the spot.
In a hole in the tree trunk, or in the ground nearby the bees' nest is
to be found.
When the beehive is opened, and the honey taken, the honey-guide will
eat the comb that is left, and apparently it is for this that the
complicated behavior of leading of man to the beehive is developed.
Wax of the honeycomb is a usual food of this species, judging by
stomach examinations, and one wonders how they get it when man is
not about to open the bee trees for them. The birds have no special
adaptation for getting into the hives; indeed their only apparent
adaptation for this habit is a thick skin, perhaps a protection against
bee stings. Perhaps, as has been suggested, other animals, squirrels,
monkeys, or honey badgers may unwittingly aid them by opening up bee
trees for their own purposes and allow the honey-guides to snatch food
for themselves.
An amusing side of the picture is that sometimes the honey-guides may
lead the honey hunter to a beehive owned by a native.
There are also records of the honey-guide leading men to big game:
leopard or lions. That this occurs is amply documented, but one wonders
whether or not this was accidental; the honey-guide leading the way
to honey perhaps by accident leads the way past the resting place of
one of these big cats so that the man stumbles over the big game and
perhaps gets the impression he was led to the animal.
OXPECKERS
[Illustration]
The lives of oxpeckers are so linked to those of large, hoofed game
or domestic cattle that in West Africa where game is scarce the birds
depend on cattle, and their range is restricted accordingly. There the
cattle are confined to the higher and more northern areas, free of
tsetse flies, from Senegal to Northern Cameroon. Thus tsetse flies help
to determine the limits of the oxpeckers' range.
Except for their nesting, which is in holes in trees, and their
sleeping, most of their time is spent on the bodies of the larger
herbivores. There they run about over the hides and legs of the beasts,
like woodpeckers on a tree. They stay remarkably close to the animals,
and even ride on them as they travel. The oxpeckers' food is largely
ticks, which it gets from the hide of the animal by working over it
with the side of its bill, shearing off the ticks with a scissorlike
action of its mandibles. But when an animal has sores or cuts or
scratches the oxpecker may peck into them, and eat flesh and blood of
its host.
Correlated with this unusual and close relationship, a modification
in the oxpeckers has taken place. There are only two species, both
African, and they are dull-colored, modified starlings. The legs are
stout, with curved, very sharp claws for clinging to the hides of
animals, and the bill, very sharp at the tip, with the cutting edge of
the mandible very sharp to aid in scissoring off ticks.
All the larger herbivores are attended by oxpeckers except the elephant
and the hippo, but the favorite seems to be the rhino, and for this
he's sometimes called the rhino bird as well as tickbird and oxpecker.
The rhino gives the bird its food, and in return the bird provides a
service of a value difficult to evaluate. It acts as a sentinel and
may warn the rhino of the approach of hunters, for which habit it is
execrated by sportsmen.
It would seem that such relationships could have developed only where
the supply of big game was large. With the introduction of cattle
and other domestic animals it was natural the oxpecker should turn
its attention to them. Here the question arose as to the attentions
of the oxpeckers being harmful or otherwise to the herds. Mr. R. E.
Moreau, formerly of the East African Research Station at Amani, has
investigated the problem. He finds that white men who own herds tend
to consider the oxpecker a nuisance; Africans tend to consider it
beneficial and some African cattle owners object to having the birds
killed; the beasts themselves tolerate the birds.
There is the possibility on the one hand of oxpeckers spreading certain
cattle diseases that are mechanically transmitted, and on the other
hand they may help reduce disease by eating ticks, the vectors of
certain diseases. Of course dipping the cattle takes care of ticks on
them, and here we see another indirect effect of civilization on bird
life. When cattle have been dipped the oxpeckers disappear from the
herd. Perhaps it is because there is no longer food for them there;
perhaps they get enough of the poison dip left on the beasts' hair to
be lethal.
WINGS IN FEEDING
[Illustration]
The obvious adaptation of a bird's wings is for locomotion; to fly in
the air. It is true that some few birds are flightless, and some like
the penguins use their wings for underwater swimming, but this does not
spoil the generalization.
Secondary uses, some with special adaptations, occur: the owl at bay
spreads its wings wide, with the effect of increasing its apparent size
and being more terrifying to a predator. The young bird, begging to be
fed, flutters its wings in a characteristic way, and the female, in
some of her mating behavior, may also flutter her wings like those of a
young bird.
In courtship the wings may play an important part in display. In the
Australian rifle bird they are held out, fully spread on each side of
the bird like a velvet curtain against which the vivid iridescence
of the throat patch stands out more vividly. The argus pheasant has
the inner secondaries greatly elongated and ornamented in a fashion
recalling the decoration of a peacock's tail and these he spreads to
show in his courtship, while the ruffed grouse uses his wings to make
instrumental music, his drumming.
Wings in geese and swans may be used in fighting, and tame birds may
severely buffet humans who take too close an interest in their young.
In the related screamers of South America the bend of the wing is
equipped with long, very sharp spurs, which undoubtedly make formidable
weapons in fighting.
In addition wings are used in at least three different ways in feeding.
The red-tailed hawk may spread its wings as it sits on its prey,
perhaps a behavior adapted to help the bird maintain its balance when
dealing with struggling prey, perhaps to help smother the struggles of
its prey.
The secretary bird of Africa is said to feed on snakes, poisonous and
non-poisonous ones, and is said to use its huge wings as shields for
its body in attacking them.
But the strangest use of wings in feeding is that practiced by a
blackish African heron. In feeding in shallow water it takes a few
rapid steps, apparently to bring it within reach of fish it has
sighted, then spreads its wings, bringing them forward until they
meet, and with the tips of the quills in the water. The head is in
the canopy formed by the wings, and apparently it is here under this
canopy that the fish on which it feeds are caught. The suggestion as
to the correlation that presents itself is that the dark canopy thrown
over the fish confuses them and makes them easier to catch.
INSTRUMENTAL MUSIC OF BIRDS
[Illustration]
Vocal music bulks large in our avian springtime chorus, but don't
overlook the instrumental music that accompanies it. The drumming of
the downy woodpecker on the dead limb of a maple near my bedroom window
is as much a part of my spring as is the cheery cheerup of our robin.
It's not that woodpeckers are voiceless that they drum. The flicker
can be called in with his particularly rich repertoire to repudiate it
vociferously. All day the downy woodpecker goes about pounding his head
against tree trunks, with his bill chiseling out wood-boring insects
to eat. What more natural when springtime comes and he wants to tell
the world, and especially other woodpeckers about it, to select a
dead limb with a nice tone in my maple tree and hammer out a rolling
tattoo--his love song and his challenge.
A DRUMMER The gray-brown ruffed grouse of a wood lot we used to have
in the Chicago area is a drummer I miss. "Thump-thump ..." he started
slowly, and then quickened to a roll that filled the forest with hollow
sound and you wondered whence it came, unless you happened to know, as
I did, that an old log in the patch of gray birch was the old cock's
favorite performing stand. There he came to roll out his invitation to
the demure hen grouse. A drummer, I've called him, yet he has no drum.
It's his wings, striking the air, that thump and build up into a roll,
its volume testifying to his great breast muscles as well as does the
whir of wings as he hurtles away through the air when I come too close.
The snipe of a nearby marsh makes music with feathers and wind, music
that is more enthralling to me than the song of the yellowthroat or
the vocal imitation of stake driving by the bittern. Circling high,
then with a change of pace, his "winnowing" or "bleating" spring song
comes drifting down. There is still room for argument, but probably
it's air rushing past the outer tail feathers that makes the sound. One
year a short-eared owl nested in the nearby meadow. Owls generally are
vocalists, even if we don't rate very high their hoots or yelps, but
the short-eared owl also has an instrumental performance. Sometimes,
when giving his mating song on the wing, a series of "toots," he
interrupted this by a dive in which he brought his wings together under
his body, with a clapping sound. It's part of the performance, but
not, as might be said, the owl applauding his own show.
Over our public school each evening in early summer a nighthawk booms.
He has a voice, and he uses it, calling "beep" as he circles high. But
the climax of his performance is instrumental, wind on feathers. He
heads down, wings high, toward the flat gravel roof on which his mate
is sitting. As he approaches the roof he moves his wings down; the air
rushing past the quills gives a tearing boom as he comes out of the
dive and mounts skyward again.
At dusk, at a damp corner of our old wood lot, in the spring, I
listened for the woodcock's flight song, a twittering of wing music as
he circles up, and sweet music, too, for a wild fowler's ears, is the
whistling of the wings of a passing pair of black ducks on their way in
the early darkness.
CONDITIONING IN BIRDS
[Illustration]
The classical experiment in conditioning and reflexes is that of
Pavlov. It consisted of sounding a bell each time food was given to
a dog. Finally the salivary response resulted even when the bell
was rung, without the food being given to the dog. The dog was
_conditioned_ to the bell. First it had responded to the food, then
to the food and the bell, and finally to the bell alone, by a flow of
saliva. The beauty of this experiment is in its simplicity, dealing as
it does with a single reflex.
Though much behavior is more complex, experiments have been worked out
to show how the environment, in a broad sense, can influence inherited
behavior. An illuminating example of this is the one I made dealing
with young loggerhead shrikes and the duration of their infantile
behavior. Young shrikes, as with young passerine birds in general,
while in the nest are fed directly by the parents, who place food in
their mouths. One of the earliest behavior patterns these young birds
perform is to stretch up with widely opened mouth, fluttering wings,
and buzzing calls, in anticipation of being fed. This we call begging.
Though typically infantile behavior, it may reappear in courtship, but
this latter we will not consider here.
Ordinarily this infantile begging behavior is discontinued shortly
after the young birds leave the nest and become able to feed
themselves. Observations indicate that in a state of nature this change
is probably hastened in part by the young birds themselves, who come to
avoid having food thrust down their gullets, and prefer to pick up the
food for themselves, and in part by the waning interest of the parents
in the young, which confers an advantage on the young who early become
self-supporting.
CASE OF RETARDED DEVELOPMENT Certain observations made from time to
time have indicated that though the age at which young birds changed
from infantile begging for food to self-supporting independence was a
fixed thing, started by instinct, certain external factors, notably the
amount of care the young received, could affect the age at which this
change occurred. Indeed there was a record of a young cedar waxwing
raised by hand who never learned to feed itself.
When I secured a brood of four young loggerhead shrikes, or
butcherbirds, the material was available to conduct a controlled
experiment. The young birds were raised together by hand to the stage
where they were ready to begin to pick up things, to feed themselves,
and to begin to abandon their infantile behavior of begging for food.
This was when they were twenty-one days old. They were then divided
into two lots and housed separately. One couple had a supply of food
kept in front of them, and hand feeding was gradually discontinued and
stopped as soon as possible. At the age of twenty-eight days they fed
themselves well, though they still begged freely when I approached. By
the time they were thirty-nine days old they begged rarely, and after
the age of forty-five days they were not seen to beg.
The other couple had no free food available at any time, and they were
fed completely by hand, the food being placed in their mouths. At the
age of twenty-eight days they had made no effort to feed themselves.
By the time they were fifty-three days old they made efforts to feed
themselves, trying to peck the food from the fingers instead of having
it thrust into their mouths, and evidently would have changed quickly
to independent self-feeding and abandoned their infantile begging
behavior. But hand feeding was continued. At the age of seven and
a half months, when the experiment was discontinued, though these
birds were capable of feeding themselves, as was seen when food was
accidentally dropped on the floor of their cage, they still begged for
food from their human foster parent.
OBJECT LESSON FOR PARENTS These four birds used in this experiment
were nestmates, and had similar heredity and early environment. The
birds in the lot which received only enough care to ensure proper
development became self-feeding, independent, and lost their infantile
begging behavior when they were about a month and a half old. The other
lot, which received an excessive amount of care in the latter part
of infancy, and were hand fed without being allowed to develop the
behavior that would have made them independent, retained the infantile
behavior pattern of begging to be fed until the end of the experiment.
They were then seven and a half months old, and their nestmates, under
a different set of conditions, had lost their infantile behavior six
months earlier.
With some birds it appears excessive care can be a conditioning factor.
It can delay the loss of infantile behavior and the acquiring of the
normal independence. Though instinctively the young shrikes tried to
develop their independent behavior, when this was not possible they
continued their dependent, conditioned behavior.
POISONOUS BIRDS
[Illustration]
Poison we know perhaps best in the plant world, whence comes, for
example, strychnine. The deadly nightshade, a common weed, is another
well-known poison plant. In the animal world we know poison best as
something that is injected into the body by stings of bees, bites
of spiders, the bites of insects, and even bites of shrews. In
addition some animals having irritating, bad-tasting, or poisonous
secretions which presumably protect the possessor from predators.
This has received most attention in the insect world, the bad-tasting
grasshoppers being examples. Toads have an acrid secretion from their
skins which deters many would-be toad eaters, and pickerel frogs have
somewhat the same thing.
The following three birds, which are recorded as having poisonous
flesh, are, strangely enough, all members of groups ordinarily
considered good table birds. Further, it seems the poisonous properties
of their flesh are not constant, but apparently depend on what they
have been eating.
The ruffed grouse of the United States is regarded by many as the
finest of upland game birds and favored by the epicure. However,
Mr. E. H. Forbush, in his monumental _Birds of Massachusetts and
Other New England States_, gives accounts to show that in winter the
ruffed grouse is known to eat leaves of laurel, which have poisonous
properties, and that there are stories of serious poisoning resulting
from eating the flesh of the birds. Such poisoning, Forbush points out,
seems to have taken place only long ago and only by winter-taken birds.
Perhaps now that it is illegal to shoot grouse in the winter when they
may have been feeding on laurel, such poisoning does not occur. This
seems an additional reason for obeying the game laws.
Pigeons in the tropics are abundant both as to individuals and as to
species and many are favored as food. However, Messrs. D. L. Serventy
and H. M. Mitchell, in their recent volume on the birds of Western
Australia, report that bronze-wing pigeons of two species are given to
feeding on the seeds of the box-poison plant, and when they have been
feeding on these seeds their entrails and bones, but not the flesh, are
poisonous to dogs and cats. The effects of eating this poison seems to
be that the dogs and cats have fits, become mad, bite at anyone within
reach, and finally die in convulsions.
During Colonel Meinertzhagen's study of the birds of Mauritius he found
that one of the pigeons there had a bad reputation from a culinary
point of view. Reports have it that some of the people who have eaten
the flesh of this pigeon suffered from extreme lassitude, while others
reported the effects as convulsions. Strangely some of the people who
reported sickness from eating this pigeon say it tastes well, while
others who have eaten it without ill effects say that the flesh is
bitter.
KINGFISHERS ON THE TELEPHONE
[Illustration]
"What color is the kingfisher? Not the American one, but the European
and Asiatic one? My husband is painting one and needs to know the
colors," a lady's voice came over the telephone. I thought quickly.
"Will it help if I explain the various kinds and colors of kingfishers
and where they live? But no, lessons on taxonomy and zoogeography
fall too flat most of the time." The lady's voice had a Central
European quality. To her "the kingfisher" probably meant the little
sparrow-sized kingfisher of the Old World scientists know as _Alcedo
atthis_. So I'd better start with that. I described the cobalt-blue
back, with darker wings, and dark bars on the crown; an earth-brown
stripe through the side of the head, paling to whitish posteriorly,
and with ocherous underparts.
"What color is the eye?"
"Brown."
"And the feet?"
"Red."
"And the nails?"
"Black."
She thanked me prettily. I tried to tell her about some of the other
kingfishers, but she said no, she had enough, and hung up.
I sighed and thought regretfully of all the other things I had ready to
tell her.
In the United States we think of the kingfisher as the belted
kingfisher, larger than a jay, with a tousled crest and a voice like
a watchman's rattle. But there are other species farther south in
the Americas, and in the Old World there are still more. The tropics
are their home. Only one species reaches Northern United States, and
only one reaches Britain. But in New Guinea, for instance, there are
about twenty-four of the ninety or so known kinds of kingfishers; the
smallest tiny as a warbler, the largest nearly crow size.
Kingfishers, we call them, but many live on the dry land, and instead
of catching fish catch insects or other tiny animals from the ground.
One large species, with a broad shovel-like bill, is even reputed to
dig in the earth to get its food of earthworms.
They all look much alike in shape. Once you overcome your surprise at
seeing a kingfisher as big as a crow, or smaller than a sparrow, you
recognize one anywhere--big-headed, large-billed birds with tiny feet
that sit up quietly much of the time. Blue is a common color, but not
all are blue. Some are generally reddish in color, some patterned with
browns, grays, and whites tinged with blue. Many are decorated with
crests, and a few species have elongated spatulate-tipped central tail
feathers that have earned the species the name paradise kingfishers.
Its voice has given one species its name: the laughing jackass, the
jackass kingfisher, or the kookaburra of Australia. "Ha ha huh huh ho
ha ha huk" in a deafening chorus has been given as a description of its
call. A. H. S. Lucas and W. H. D. Le Souëf, no doubt with tongue in
cheek, record that "_on dit_ that the jackass has been heard to laugh
while a cicada [it had eaten whole] has been skirring inside him."
CLASSICAL ALLUSIONS Halcyon, Alcyone, and Ceyx appear in the scientific
names of kingfishers. Scientific names make the layman shudder. Latin,
he says, and if he's told they're not Latin, but rather Greek, it
doesn't help any. But once you know the story of Halcyon (or Alcyone)
and Ceyx, the names stick in your mind. In ancient times Halcyon was
the daughter of Aeolus. And in grief for her drowned husband, Ceyx, she
threw herself into the sea. The gods, out of compassion, changed both
into kingfishers. Halcyon was also used by the Greeks as a name for the
kingfisher and it was fabled to make its nest on the sea, and to quiet
the waves for its incubation period. Poets still use Halcyon for the
kingfishers in reference to calm, happy, peaceful days, Halcyon days;
the sort of days in which the kingfishers can nest on the quiet waves.
The lady had not waited for all this. She had gone. I would have liked
to see the picture her husband was painting when it was finished.
ON IDENTIFYING SEA SERPENTS
[Illustration]
The lock ness monster reappears periodically in the newspapers. This
monster seems to belong in the general category of "sea serpent." As a
museum zoologist I've had little to do with such things. The stock in
trade of a museum is specimens and if someone sends us a "sea serpent"
(and I don't mean a water snake or a sea snake), we'll identify it.
If it doesn't have a name we'll give it one and make a place for
it in our classification. Until then we are aloof. We've had some
little experience at times with "sea serpents" and the following will
illustrate the sort of investigation and the results that we've had.
Years ago Sir Frederick Jackson was an administrator in East Africa.
In addition to his official duties he was an enthusiastic and an able
naturalist. So when a "sea serpent" was reported there he investigated.
IN KENYA The sea serpent was said to frequent Lake Naivasha in the Rift
Valley of Kenya Colony. Up until 1909 there were many rumors of it, and
Europeans had seen it with their own eyes. It always appeared on the
lake about the same time each day, about five o'clock in the afternoon,
always about the same distance from the shore, and was always traveling
in the same direction, from north to south. All descriptions agreed
that it was long, black, and reptilelike, and that it kept appearing
and disappearing on the surface of the water at short intervals.
Sir Frederick kept watch with one of the people who had reported it.
And, sure enough, what appeared like a long black reptile appearing and
disappearing, or like a school of porpoises, rising and disappearing,
came into view. But Sir Frederick had binoculars and was able to make
out that what to other people had been a long black reptile was in
reality a long line of white-breasted cormorants in flight, on their
way to their roosting quarters. As they flapped steadily along they
were plainly evident, to the naked eye, as a moving black line; as they
paused in their flapping and sailed on motionless wings they became
invisible to the naked eye, though, of course, still visible through
the binoculars.
IN NEW GUINEA Once, for a few startled moments, I thought I had a sea
serpent before my very eyes. It was on the middle Fly River in south
New Guinea. We were camped on a bamboo-covered bluff overlooking the
river. Though about one hundred miles from the mouth, the tide made
itself strongly felt here, and there was an abundance of driftwood.
This driftwood, varying from freshly uprooted trees that had fallen
into the river to waterlogged timber that had been long in the river,
went up and down on the tide until it got out in the main channel and
so on to the sea. One day at lunch, sitting in front of my tent, I
was idly watching the driftwood. One piece in particular caught my
fancy. Apparently it was the root of a partly submerged log, projecting
about three feet above the water, and curved at the end so that it
looked like the neck and head of a reptile with a casque on its head.
Knowing it was a waterworn root, in fancy I even saw its eye. I called
my companion's attention to it, as here was as close as we were ever
likely to get to a sea serpent. Then, the "head" turned. It was alive.
For a few startled moments it was a sea serpent. You can imagine our
amazement at having a piece of driftwood that we had in fancy turned
into a sea serpent come to life. Investigation became the order of the
day. The binoculars that were constantly at hand were trained on it.
The reality came as a further surprise. Our sea serpent was the head
and shoulders of a cassowary which was swimming the river. Later I
found that these large, ostrichlike birds, which have a large casque on
their heads, are well known to swim, but I didn't then.
This seemed an ideal opportunity to collect a specimen. These birds may
weigh up to 150 pounds. When shot in the forest there is the question
of lugging them perhaps miles to camp. Here was one swimming up to our
door.
We sat quietly waiting for it. But our native boys had seen it too, for
next I saw them rowing the dinghy to it. An oar was brought into play
to stun it. And then both the boys and ourselves found out something
else. Dead cassowaries sink. When the bird was stunned by a blow of an
oar, it disappeared below the surface and was never seen again.
CONSERVATION OVER THE TELEPHONE
[Illustration]
Richard Orr, the _Tribune_ reporter, called me one day about bronze
grackles. It seems that the Chicago _Tribune_, in their "Day by Day
on the Farm," had told about the grackles on the _Tribune_ farm. A
_Tribune_ reader wrote in, expressing surprise that grackles were
permitted on the _Tribune_ farm and gave details of destruction by
grackles of other birds, personally observed. What were the facts of
the case? Should grackles be tolerated? Or should they be eliminated?
Orr wanted to know.
This is the sort of question that is difficult. It is important,
too, for it involves basic conservation issues. And there is no
sharp, clear-cut yes-or-no answer. The question as to the grackle's
character reminds me of the character of Moses, as explained when I
was in school by a professor of the Bible: The black was there and
the white was there; Moses was a character sketch in gray. And so
with most creatures. They're both good and bad from our standpoint.
Grackles certainly do kill other birds at times, and interrupt the
nesting of some of our favorite songbirds. And yet, liking birds as I
do, I tolerate them in my garden. On a trumpet vine on our garage in
Chesterton, Indiana, one year we had a grackle build its nest on top of
a domed English-sparrow nest. The young of both sparrows and grackles
hatched about the same time, and the two families, within six inches
of each other, were successfully raised without friction between the
parents.
Quite evidently grackles are not always killers of other birds. As to
robins or grackles being the "better" birds, if we had a robin's nest
that we prized, and the grackle killed the young in it, the grackle
would be "bad." But if we were an inquiring farmer, and had to weigh
the grackle against the robin, we might find the grackle "good" and the
robin "bad." The grackle feeds its young vast quantities of insects
harmful to the gardener; the robin sometimes seems to specialize in
earthworms. Earthworms are beneficial to man, passing through the
earth, making air and water more accessible, and, by passing earth and
vegetable matter through their intestines, enrich the soil.
The house wren that warned the _Tribune_ reader when the grackles
were about is often prized as a garden bird; it is bold, saucy in
appearance, and a vigorous songster. But it is also well known as a
quarrelsome bird, prone to punch holes in the eggs of its neighbors,
and it also may fill up with sticks nesting boxes so that other birds
cannot use them.
The above was the gist of what I told Orr, and appeared in the May 5,
1950, _Tribune_.
Thinking of it afterwards, as is usual, I thought of many other things
I could have said, and perhaps made more clear that no bird is all good
or all bad, from our human point of view. Their relationships with
the rest of the landscape are complex. I like to see butterflies flit
about my garden. But butterflies are caterpillars at one stage. And
caterpillars may eat some of the things in my garden. But some birds
feed on caterpillars. If I eliminate the caterpillars because they
eat the plants I like, at one stroke I eliminate the source of the
butterflies I like, and food for some birds I also like.
Perhaps the partial answer, if answer there be in this imperfect
world, is summed up by moderation: I can have some butterflies, some
caterpillars, some plants, and some birds in my garden. If one becomes
too abundant and interferes with the others, I prune it. Maintaining
some sort of a balance, we can have some of each.
BIRDS WASHING FOOD
[Illustration]
We not only wash ourselves and our clothes, but certain items of our
food are regularly washed, as spinach, to get the sand out of it.
Washing has been so important in our society that we've coined the term
"Cleanliness is next to godliness." Possibly we've the snobbish idea
it's a strictly human trait. Among other animals we don't expect to
find water used for such cleanliness, and the raccoon, who does wash
his food, is considered a sort of biological oddity.
But when we come to birds we find a surprising number of them that wash
their food.
The dipper of our Western mountains in Oregon has been seen to wash
insects and grubs before feeding them to the young birds. The parents
held the food crosswise in the bill and the head was twisted rapidly
from side to side in the water. Not until then was the food taken to
the nest for the young.
The scene shifts to Africa. Four buff-backed herons were feeding on
a flooded lawn at Gezira, Egypt. One of the birds captured a large
insect, apparently a large black beetle. Holding the insect in the tip
of its bill, the bird walked to the water, immersed the beetle three
times, shaking and fumbling with it the while, and then swallowing it.
Then in Britain came a whole host of records, after an observation
in Holland in 1946 of curlew sandpipers washing food. The birds were
probing the dry mud at the edge of a little creek. When one of the
birds got a small sand worm, it at once ran with quick steps to the
creek and stepped into the shallow water, where it dipped the worm a
few times into the water before swallowing it. Then it trotted away
for more. The editor of _British Birds_, the journal in which this was
published, suggested that this might be a more common habit than the
scanty published records would indicate, and invited observations.
A spate of records resulted in the succeeding numbers of the journal:
a whimbrel washing crabs; a snipe, earthworms; godwits washing their
food; with curlews it was reported to be normal; dunlins, greenshanks,
redshanks, ringed plover, and oyster catchers were all reported doing
this until it appears that with the group of birds we call shore
birds--sandpipers, snipes, plovers, and their relatives--it may indeed
be normal. The details of the observations strongly suggest that the
reason for the washing, in many cases at least, is the same one that
underlies our washing spinach; to get the sand and mud out of it.
HOW ANIMAL VOICES SOUND TO FOREIGN EARS
[Illustration]
When in El Salvador in 1951, I found that the common barnyard animals
had much the same voices as the ones with which I was familiar in
the United States. But when I saw their utterances written down it
was another matter. The voices written in Spanish sometimes looked
as different as the names of the animals written in Spanish. Take
the donkey, for example (or _burro_, as they call it in Spanish). In
English we call its "song" "Heehaw!" In Spanish they wrote it for me,
"Aja! Aja! Ija! Ija!" There were a number of German scientists at the
Instituto Tropical de Investigaciones Científicas, where I was working,
and for comparison I asked them to write for me what the same animals
said in German. The burro (_Esel_, they call it in German) says,
"_Ihå! Ihå!_" in German. Despite the difference in the appearance of
these words, when they were pronounced by the various nationalities
they sounded very similar. Compared with the original assinine
pronunciation, the Spanish version was awarded the prize for being the
best rendition of the beast's voice.
The cat's "_Miau, miau, miau_" in Spanish, "_Miau, miau_" in German,
and "Meow" in English were all very similar in appearance as well as
sound. The duck's voice came out differently. In Spanish it was "_Cuá,
cuá, cuá_," in German "_Wack, wack_," and in English the initial "Cu"
or "Q" sound of the Spanish, and the final "k" sound of the German
are united into "quack." The hoot owl came out much the same in
pronunciation, though it looked different in the Spanish "_Ju_," in
German "_Hu_," and in English "Who."
The cow's, the pig's, and the frog's voices were also rather similar
in the three languages: the cow's in Spanish being "_Meu, meu,
muuu_," in German "_Mŭh, mŭh_," and in English "Moo"; the pig's
"_Grup-grup, wink_," "_Óŭik, Óŭik_," and "Grunt, oink"; and the frog's
"_Cruac, croac, croac_" "_Quak, quak_," and "Croak." The barnyard
rooster has a difficult voice to transcribe in letters. In Spanish
it was "_Quiquiriguiiii_," in German "_Kickeriki_," and in English
"Cock-a-doodle-do." After listening to the various renditions by the
various nations I could see how each rendition came into being, but as
for deciding which was closest to the original I hesitated to choose.
When it came to the dog, the discrepancy was surprising: in Spanish
it was "_Guán, guán, guán_," in German "_Waŭ, waŭ_," and in English
"Bowwow." The German and the English are close enough. But though I
went outside and listened to the dogs in Salvador, never did they seem
to say, "_Guán, guán, guán_," though I must admit that neither did they
seem to say, "Bowwow."
SIGHT IDENTIFICATION
[Illustration]
Sometimes when I'm trying to decide whether the birds of the Cameroon
Mountains of West Africa are the result of one invasion and variation
_in situ_, or of two invasions, or whether the Himalayan red-billed
choughs of Ladak are different from those of Nepal, or how the molt of
the cassowary resembles that of penguins, I am called to the telephone
to identify a bird someone has seen.
The chances are it's a starling. I've not kept a record, but I fancy
half the questions are on identification of starlings. In the distance
starlings are black, and people know them. But close up, where details
can be seen, they puzzle people with their variety. The young may be
dull brownish; the adults may be speckled in the winter; in the spring
the speckled tips of the feathers wear off and they're all black. But
the black is iridescent, and in sunshine glitters purple or greenish.
And the bill color changes too: it becomes yellow in the spring.
Sometimes it's surprising how you can spot a bird from a brief
description. Take this one: a bird that sits with its stomach on
the ground, and has a big mouth, and long whiskers; a whippoorwill
obviously. Or take this one: a bill like a chicken and with flat feet
at the back; obviously a pied-billed grebe.
There was one that absolutely stumped me for a day. The lady said
it had a bill like an eagle, and a tail that stuck up. For the rest
she was vague. Often habits, actions, or habitat are a help to me in
placing a bird, but I could get nothing to help--not even where she had
seen it. I admitted I couldn't help her. The next day someone brought
in a picture puzzle out of a newspaper, and there, right in the center,
was my bird. It was a dodo! We don't mind helping people learn things,
indeed we consider it part of our job, but to help them work puzzles is
too much!
MY LESSON Sight identifications of most students probably contain
errors. On common species it's not important, as quantitatively
they cancel out. But when a bird tripper, anxious to make a new
record, wants me to help him decide he saw an exotic tern, I'm very
careful--I've had experience. Rarities have to be checked on all
points, not identified by elimination or on a few key characters. One
of the best lessons of caution I had in New Guinea. It was in the
mountains. Each morning I hunted in a forest where I'd found a new
genus of bowerbird. Anything might occur, I thought. Then I saw flying
through the treetops what could only be a magpie. A long-tailed, black
and white bird, its pattern was unmistakable. There was nothing like it
known from New Guinea. It would be an extension of range from Asia. Or
it was a new and unknown species. Anyway I needed it as a specimen. But
it was shy and eluded me. Morning after morning I haunted the forest.
Finally I got the bird. And it turned out to be a partly albinistic
specimen of a common, black, long-tailed bird of paradise. The abnormal
white areas in its plumage had fooled me completely. But it helped
teach me caution as to sight identifications.
One of my Gary friends, Mr. Raymond Grow, who is a keen bird student,
has the proper approach, as his identification of a winter duck showed.
There were a number of unusual winter birds that season (1951-52):
brown-headed chickadees, pine and evening grosbeaks, and red-breasted
nuthatches, all from the North, were present. It was the sort of winter
one expects other rarities from the North.
DUCK CAUSES CONFUSION Mr. Grow had seen at the edge of Lake Michigan a
duck he didn't know; it was boldly patterned in black and white, a big
duck. An immature male eider seemed the only possibility. He came into
the museum and we went over specimens, noting the difference in the
shape of the head between the king and the common eider. He studied the
descriptions and the plates. Nothing quite fitted. Unsatisfied, he went
back to Michigan City, found the duck again, and suddenly realized
it was a muscovy duck, partly albinistic, and escaped from someone's
barnyard.
It's not the first time a muscovy has caused confusion. Only a
year or so ago we had a duck sent us from the Philippines that our
correspondent wrote was shot swimming in a river with a Philippine
mallard and surely represented a new species. But it turned out to
be a muscovy whose original home is tropical American but has become
domesticated and transported by man to far parts of the globe.
Occasionally birds escape and take to the wild, even as this Philippine
bird had done.
GREEN HUNTING JAYS TURN BLUE
[Illustration]
Sometimes in "working out" a bird collection things get dull. In
identifying the specimens, and writing down why they are this species,
or that species, or subspecies, it seems routine; as though it were
simply routine putting things in the categories ready for them.
Such was my feeling one day as I worked over Himalayan jays and magpies
from Nepal. I'd done the yellow-billed blue magpie, and the red-billed
blue magpie, which both fell into their places smoothly. Then I got
out the literature, the pertinent keys, and descriptions for the next
species, the green hunting jay. It's a beautiful, pale, apple-green
bird, with a green crest, and set off by dark red wings. It checked
with the descriptions, and I wrote _Kitta chinensis_, its scientific
name, on the label. Then, to check the species' identification and to
determine the subspecies, I turned to the collection, to the birds from
India, Siam, and north Indochina, which should all be the same.
I pulled out the drawer--and blinked at the jays, rows of them; all
pale blue with brown wings. I looked at the name on the case, on the
tray, and the name on each specimen. They all said the same, _Kitta
chinensis chinensis_, and it was the bird described as green, like my
new specimen. It was uncanny. The new green specimens and the old blue
ones were identical in size, in structure of bill, crest, feet, tail;
they must be the same. And they were. The book, I found, described
how the colors changed with age, and in John Gould's magnificently
illustrated folio, _Birds of Asia_, published in 1861, he had the
green hunting jay depicted both as a green bird with red wings and, in
the background, a "blue" green hunting jay like our museum specimens.
When alive, and when freshly killed, the birds are green. But with the
passing of time the green changes to pale blue, and the red wings to
brown wings. Probably my new specimen, now a year old, is less green
than it was when fresh. And when twenty years old, like our museum
skins, it will be blue too.
The riddle was solved, and it fits into a well-known phenomenon,
"museum age" or post-mortem change. "Foxing," we call it for short. We
see it in the male American merganser, where the lovely rich salmon
color of the fresh bird becomes plain white. The emerald cuckoo of
Africa has vivid rich yellow under parts when fresh, and this too
becomes dingy white. Gray Canada jays become more brownish. Birds that
are olive or other shades of green tend to become more olive; brown
birds tend to become more russet or foxy (hence the term "foxing"). We
keep all our specimens in dustproof, lightproof metal cases. The change
is not caused by fading. Apparently it's a change in the pigment,
perhaps from oxidation.
Taxonomists, the men who classify and name birds, have been fooled by
it. Old skins used to represent the birds of an area may give a quite
different idea of what they are like than do fresh skins, and when
skins of different age are compared, the conclusions may be wrong.
Foxing is one of the pitfalls for the unwary taxonomist, and something
he has to guard against.
HOW BIRDS USE COWS AS HUNTING DOGS
[Illustration]
The sportsman out for quail or woodcock uses dogs to drive out the
birds for him. Starlings and cowbirds about Chicago use the same
principle in hunting grasshoppers. Instead of dogs they use cows,
though of course the cows are intent on something else and presumably
unconscious of the fact that they're helping the birds.
As the cow grazes slowly across a meadow, it scares up grasshoppers
close in front of it. The cowbirds and starlings take advantage of
this. Instead of covering the meadow on foot, constantly alert for a
sitting grasshopper, or to chase one they flush, the birds keep with a
grazing cow. They take up a position by the head, or a foot, and catch
the insects the cow disturbs. The cow is so much larger than the bird
that it is likely to flush more insects. The grasshoppers on the wing
are much easier to see than when at rest in the concealing grass, and
some fly directly toward the bird. Too, the grasshoppers fleeing a cow
are less likely to be alert to other dangers.
CONFIRMED BY OBSERVATION The advantages of this to the bird are
obvious. But we've just assumed they were, and we had no data on the
relative efficiency of the two methods of hunting. A few years ago,
however, while in El Salvador, I was able to get quantitative data
proving that using a cow as a beater was advantageous, as we suspected,
and showing how much more effective it was, something we did not know.
The bird concerned was not the starling, which does not occur there,
or a cowbird, which occurs but consorts little with cows, but was
the grove-billed ani, a black cuckoo about twelve inches long of
the tropics of Central and South America. Like our starling and our
cowbird, it kept with cows, catching the grasshoppers and other insects
that flew up. Both anis and cows were common in the grassy fields about
our headquarters in San Salvador. We decided, my son Stanley and I,
to watch anis with cows for a few hours, and then without cows for a
few hours; thus getting the average rate for each type of feeding. We
quickly found it wasn't as easy as that. Something always happened;
even on the levelest and most open fields the birds were constantly
disappearing behind a tuft of grass, or in a hollow, or, if nothing
else, behind the cow's head or feet. Then, too, the ani we elected
to watch wouldn't pay attention to the job in hand. It would wander
off, or go to sleep. And sometimes, when we were about to discontinue
watching a somnolent bird, it would snap up an insect. Perhaps it
had been watching all the time. Finally we found we had to record
observations of many short periods, of from three to fourteen minutes
each, and add them together.
By dint of much patient watching we got our data. In the dry season
when insects were scarce and the grass short, it took an ani, hunting
alone, two minutes on the average to find an insect. In the same length
of time hunting with a cow the catch averaged three insects. Thus
hunting with a cow as a beater was three times as effective as hunting
alone.
The effect of the change of the season in abundance of food for the ani
was very striking. In the wet season the grass began to grow fast, and
insects became common. Then the anis had an easy time. Without a cow
an ani averaged between three and four insects a minute, more than six
times as much as in the dry times. There was less incentive to use a
cow as a beater, with food so abundant, but when the ani did so, its
rate of finding insects was still higher: between four and five insects
per minute. In a table it looks like this:
_Average Number of Insects Per Minute Found by Ani Feeding_
WITHOUT COW WITH COW
Dry Season .5 1.5
Wet Season 3.4 4.7
But the three-times-greater-results in a given time in the dry season
do not tell the whole story as to the effectiveness of using a
beater. When an ani was hunting by itself it walked about, covering a
surprisingly large amount of ground. When using a cow as a beater, not
only did it catch more insects in a given length of time, but it also
walked about much less, saving a great deal of energy.
This is not true co-operation between cow and bird, for they're not
working together toward a common end. It's not exploitation of the cow
by the birds, for the cows lose nothing. It is closer to a form of
harmless parasitism, for the ani profits from the activities of the
cow without either harming or helping the cow. It also illustrates
how sharp birds are--ready to take advantage of any factor in their
environment that will help them get their food.
EARLY BIRD LISTING
[Illustration]
I wonder how many of the people who go out making lists of spring birds
know that bird listing goes back to ancient times. It's a modern sport,
but earlier bird watching was serious, and a competitive listing of
birds played a part in as important an event as the selection of the
site of the city of Rome.
The story, as Plutarch tells it, is that Romulus wanted the city on
what became known as Roma Quadrata; Remus wanted it on the Aventine
Mount. As was the custom in those days, they concluded at last to
decide by a divination from a flight of birds. The twins placed
themselves apart at some distance and watched. Remus, they say, saw
six vultures, a truly notable flight; Romulus saw twelve and from this
rare and unusual occurrence Romulus' choice of the site for the city
was accepted.
VULTURES HIGHLY REGARDED Partly from this the vulture became chiefly
regarded by the Romans in their divinations from birds. But even before
this the vulture was highly regarded. Hercules, it was said, was always
very joyful when a vulture appeared to him upon any occasion. He
considered it the least harmful of creatures; not pernicious to corn,
fruit tree, or cattle, it never killed or hurt any living thing. It
was also thought not to eat other birds, a weighty point in its favor,
as Plutarch quotes from Aeschylus, "What bird is clean that preys on
fellow bird?" And apparently its deciding claim to esteem was its
rarity and infrequency, which gave rise to the opinion in some that it
came from another world, an opinion foisted by the soothsayers of the
day.
Earlier yet, birds played a part in Rome's history. Plutarch warns
that some give you mere fables of the origin of Rome, but it is
widely current that Remus and Romulus, fathered by Mars, the God of
War, were exposed in a remote place to perish. This would have taken
place, but for a she-wolf that nursed them, and birds of various sorts
that brought little morsels of food which they put into their mouths.
Some, however, hold the belief that not birds of various sorts but a
woodpecker was the bird that constantly fed and watched the twins, and
even in Plutarch's time the Romans still worshiped and honored the
woodpecker for this service to the founder of the city.
BATTLE OF THE SEXES AND ITS EVOLUTIONARY SIGNIFICANCE
[Illustration]
I used to think that the battle of the sexes so ably portrayed by James
Thurber was artificial, a man- and/or woman-made thing. But recently
I've come to see it as old--probably as old as sex itself in the animal
world.
Under the severe tide, "Secondary Sexual Characters and Ecological
Competition," in a paper from the Bird Division of the Chicago Museum,
I've outlined the possibility of competition for food, between
the sexes, being a factor in evolution, responsible in part for
characteristics of structure and traits that distinguish them.
In circles that discuss evolution the idea is current that food
competition is important between species. It may even be stated as a
rule: two species with the same food habits cannot live in the same
place. Competition drives one out, unless they have different food
habits. These differences seem especially evident when you look at
closely related species, and they are accomplished in a variety of
ways. A habitat difference is very common. The long-eared owl hunts in
the woods--its cousin, the short-eared owl, hunts the meadows; the song
sparrow favors the drier shrubbery while its cousin, the swamp sparrow,
lives in wetter shrubbery.
THE SIZE FACTOR Sometimes the difference is accomplished by size; take
the downy and hairy woodpeckers of our wood lots, very similar except
that one is larger and is adapted for larger prey, the other smaller
and adapted for smaller food items. Sometimes they feed differently,
as the Baltimore oriole, which picks flowers and pecks through their
sides, while the orchard oriole probes into flowers as they hang on the
branches. Thus more individuals of several species live in an area.
When a pair of birds "sets up housekeeping" and starts "raising a
family" they can no longer drift about, looking for easy living and
places where food is plentiful. Their wanderings are restricted by
having a fixed point, the nest, as their center of interest. Two
individuals must draw on the food supply from an area about the nest.
Competition would be extreme, and, if there were a scarcity, perhaps
critical.
We know how different the sexes may be; how different the rooster is
from the hen in our domestic fowl, or the drake and the duck in the
mallard, or the red male and the green female of the scarlet tanager.
These sexual differences have mostly correlated with display and
mating. But logically there should be differences in feeding behavior
and adaptations between the sexes.
The basic idea is contained in the old nursery rhyme:
Jack Sprat could eat no fat,
His wife could eat no lean;
And so between them both,
They licked the platter clean.
The two birds of a mated pair, limited to a single area, could be
expected to have different food preferences or adaptations for getting
it. And we find that there are cases of this. The most striking is
that of the huia from New Zealand, of which I've written in a Chicago
Museum bulletin. Both sexes have similar food preferences, especially
wood-inhabiting insects, but they get them in different ways. The male
has a short, straight, stout bill for digging out the wood-boring
grubs, woodpecker fashion; the female has a much longer, slender, and
curved bill for probing into holes for them, creeper fashion. The
female may get grubs in wood too hard for the male to chisel. They
supplement each other.
DIET VARIATION BY SEX It is possible that further study may show more
sexual differences to have a feeding advantage; the larger size of
female hawks fitting them to take larger prey; the smaller size of
certain female songbirds fitting them for smaller prey, the smaller
bills of female hornbills, the straight bill of the male western grebe,
and the upturned bill of the female. Perhaps all are of advantage to
the species in giving each sex slightly different advantages in getting
food.
Selection could have its effect in the populations with most sexual
difference in feeding habits being most successful in raising and
leaving progeny. Thus, slowly, differences between the sexes would
accumulate. However, it must be kept in mind that this sort of
evolution would be limited. The drifting apart of the sexes would be
checked by the necessity for their coming together periodically for at
least a short period, at nesting time.
WATER IN THE DESERT
[Illustration]
Water is a precious thing in the desert. Without it no life is
possible. When rains come plants spring into vigorous growth. During
the long stretches without rain they rest, some as seed, while some
plants store water in root systems, or in large trunks. Animals have
developed a number of ways of surviving long dry spells in arid country.
Among mammals the kangaroo rat of our Southwestern desert seems able to
get along without water. This is caused by an arrangement within the
body whereby the necessary water is manufactured within the animal from
other foodstuffs: metabolic water.
The accessibility of drinking water in a desert may be the determining
factor in whether or not some birds can survive there. The nests of
Gambel's quail must be close enough to drinking water for the newly
hatched young to walk there, else they perish of thirst. It has
been said that newly hatched chicks of the related valley quail of
California cannot travel more than a few hundred yards from their
hatching places without water. Broods hatched farther away are doomed
to die.
Sand grouse, relatives of the pigeons that have adopted the general
appearance and habits of quail, live in the Old World, primarily in
arid or even desert areas. Where they occur their daily traveling to
water is a well-marked phenomenon. Their flight is swift and powerful,
and though they may traverse long distances of barren, inhospitable
country to watering places, their punctuality in arriving at water,
morning and evening in some species, is remarkable.
But what of the young of these desert dwellers that need water? A most
unusual situation exists; indeed it seems to be unique. The old birds
bring water to the young! This has long been recorded, but as recently
as 1921 it has been questioned. However, Mr. Meade-Waldo's observations
on birds in captivity seem to definitely establish the custom, and its
methods.
PARENTS CARRY WATER Both birds incubate the eggs, the male by night,
the female by day, and both parents care for the young. But it is the
male only that brings water to the young. He rubs his breast violently
up and down on the ground, and then, his feathers awry, he gets into
his drinking water and saturates the feathers of his under parts.
Then, in captivity, he would run to the hen, make a demonstration,
whereupon the young would run out from under her, get under him, and
suck the water from his feathers. This they did by passing the feathers
through their bills, continuing and changing about until the supply was
exhausted. It was found that until the young can fly they take water in
no other way.
This was in captivity. Presumably in the wild the process is the same,
the adult flying with wet under parts from the water hole to the
resting place where the young are under the care of the female.
The similarity of the young sucking water from the feathers to young
mammals suckling their mother has been pointed out. But another and a
truer similarity exists: that of the young sand grouse getting water
from the feathers, and young quail getting water from dew-wet leaves in
areas where dew is heavy and there is but little surface water.
BIRD GRAVEYARDS
[Illustration]
The best-known stories of animal graveyards are those of elephants.
But when I asked the curator of mammals about them the answer I got
was little better than a snort. Apparently the evidence for them is so
vague that it's little better than a myth.
But in birds we have a few bits of evidence from far-scattered places
that occasionally such things as graveyards exist.
In the antarctic Dr. Robert Cushman Murphy found on the island of South
Georgia a place where Johnny penguins went to die. It was in a lake
in a coastal range of hills. The lake bottom was thickly strewn with
scores of penguin bodies, all of which had apparently died a natural
death. The icy water, Murphy thought, might preserve them for years.
The hills, away from the sea, seem a surprising place for the graveyard
of such aquatic birds as the penguins, but it correlates with another
peculiarity of their mental makeup. They like to nest on high land, or
at least far from the sea. The blind instinctiveness of much penguin
behavior is well shown by these birds when there is no high land on
their nesting island. Then they may nest so far from the beach on which
they land that they are close to the water on the other side. Yet they
always returned to the sea by the long route, never taking the shorter
route.
Another aspect of this preference for land distant from the sea is
shown by their behavior when threatened with danger from man or dog.
They flee away from the sea, back onto the land, when safety for them
actually lies in the sea. Presumably this fixed behavior dates back to
the time when the seal that is called the sea leopard was the penguin's
main enemy. Then the sea held their only danger. With man's arrival the
situation changed, but only after considerable experience with man do
the birds change this behavior.
Apparently, when the time came for the penguins in this South Georgia
graveyard to die, they followed their age-old pattern, climbing to the
high country and away from the sea.
IN A HOLLOW TREE In a hole about eighteen inches in diameter and twelve
feet deep in the trunk of a wych elm in Hants, England, Ursula M.
Grigg reports finding the bones of at least ninety jackdaws, thirteen
starlings, six green woodpeckers, and twenty-five stock doves. All the
remains were clean, and not much broken or decomposed. The idea that
these bones were the remains of owls' or other predators' feasts was
discarded for a number of reasons; as was the idea that this had been
a natural trap, the birds entering to roost or nest and being unable
to escape. The most tenable idea seems to be that this was a favorite
roosting place in winter, and that during the severe weather old and
weakened birds, roosting there, succumbed and added their bodies to
this communal grave.
ON AN ISLAND Another instance comes from the little Cape Verde Isle of
Cima in the South Atlantic. A photograph in the _National Geographic_
magazine for 1927, Vol. 52, P. 27, has the caption that this island is
unique and uninhabited and covered with the tiny bones of millions of
petrels which in ages past have come here to die. Certainly the plate
shows an amazing litter of bird bones on the tiny plateau of this islet.
Petrels are mostly pelagic birds, coming to the land only to nest on
isolated islets. Can this "graveyard" be merely the normal accumulation
of the bones of the nesting season mortality, or can it be that the
birds actually come here to die?
ANIMAL GARDENS
[Illustration]
Best known of the "gardens" and "animal husbandry" of the lower animals
are those of the ants; the aphis kept by the ants for the sake of a
sweetish secretion, and the underground fungus garden of the ants. In
the vertebrates I know nothing comparable to this, but we do get a
number of cases where there is a definite relation between the animals
and the growth of vegetation.
It has been said that in the antarctic the nesting colonies of some
penguins are detrimental to the vegetation. The constant passing
and standing of the birds on the limited areas of soil preclude the
growing of vegetation over sufficiently large areas to be an important
factor in hindering plant growth. But the reverse is true of the
Johnny penguin in the Falklands, where it is sometimes known as the
best farmer in the country. The Falkland Islands, off southern South
America, are cold, wet, and windy. Sheep raising is one of the main
industries. And the Johnny penguin helps to provide better pasture
for the sheep. The birds nest in colonies and their droppings help
to enrich the land so that the grass grows taller and richer. Rather
than using the same area for their breeding colony each year the birds
select a new, clean area at the beginning of each breeding season, so
that they improve the ground over a larger area.
From the arctic comes another example of a relationship between bird
and plant. On the arctic barrens, here and there, are large boulders,
erratics left by the glacier that covered the land in times past. And
on these boulders, and here only, one finds patches of bright yellow
or reddish lichen known to scientists as _Xantheria_ or _Xanthoria_.
Apparently its presence is owed to the fact that these boulders are
the lookout places of snowy owls, hawks, and other birds. Their
droppings, falling on the rocks, provide the nutrient layer necessary
for the growth of the lichens. It is probable that these lichens are
transported from place to place by the birds carrying the soredia on
their feet. In recognition of the close relationship between these
lichens and birds an ecologist has coined the rather formidable term
"ornithocoprophilous" to express the relationship.
Also in the arctic are the arctic-fox gardens. The arctic fox often
makes its burrows in sandy places, and about the entrance to the
burrow accumulate remains of former meals, fox droppings, and suchlike
animal debris. This in time enriches the soil and the vegetation
there grows taller and more lush than elsewhere on the barrens. This
lush vegetation attracts the small, mouselike arctic rodents, the
lemmings, that feed on green, succulent vegetation. There is of course
one further step in this chain. One of the important foods of the
arctic fox is the lemming, which he thus brings to his door by the
richer vegetation he unwittingly causes to occur there. A charming
arrangement, one of the old naturalists called it.
DROPPING THINGS
[Illustration]
The story is well known, being recorded by Pliny, of how the poet
Aeschylus came to his death through a bird mistaking his bald head
for a rock and dropping a turtle on it. The bird was evidently the
lammergeier or "lamb vulture," one of the largest and most magnificent
of the Old World birds of prey; nearly four feet long. In the Atlas
Mountains of North Africa its normal food is turtles, and these it
cracks open, so that it can get at the meat, by carrying them up into
the air and dropping them on a rock. Now it lives in the Himalayas
and in Africa, having been almost if not completely exterminated from
Europe because of its alleged predation on sheep. Not only turtles but
bones are treated in the same manner, to get at the marrow. Though
the habit is well known, it is surprising how difficult it is to find
a firsthand description of it. So far I know of only one description
written by an eyewitness. And yet, in East Africa recently a stony
mountaintop was found littered with broken bones that seemed to be the
result of the lammergeier's habit.
GULLS DO IT As I have mentioned, gulls open clams and mussels in this
way; and crows, which are among the most intelligent of birds, do it
also. They pick up the mussels left exposed by the falling tide, fly up
above a hard stretch of beach, a big rock, or a stretch of nearby paved
road, and drop the shellfish there. While in general this practice is
restricted to a few groups of birds, it is practiced by them in many
far parts of the world. The Pacific gull of Australia, widely separated
from its near relatives, has the same maneuver for opening shellfish as
has our herring gull.
It's hard to understand just how this habit came about. One can imagine
that some birds found it out by accident when flying about with a
stubborn "nut" they were unable to crack. Or perhaps it was in play
they found it. The raven is known to fly about carrying and dropping
things in play.
SPARROWS DO IT TOO Often, to find a background if not an explanation of
a habit, we look about to see if it's used in some other connection.
I've already mentioned the play of some of the crows. Only one other
"dropping" habit has come to my attention, and that is a single
record for the very common house sparrow. Edmund Jaeger writes that
in Nebraska, and again in Riverside, California, he saw house sparrows
on gravel roofs, dropping small stones over the edge. The pebbles, or
small bits of crushed stone, were carried to the edge of the building
by the sparrows, dropped, and as each pebble was dropped the sparrow
turned its head, apparently the better to watch or listen to the pebble
fall and strike. No obvious utility appeared in these actions. It, too,
looked like pastime. Perhaps there was no better reason behind them
than that behind small children dropping stones down a well.
LEARNING BY BIRDS
[Illustration]
Of course birds can learn. Indeed there's a trite saying that no animal
has been discovered so low that it cannot learn. One of the simplest
cases of learning is shown by parts of some experiments I carried out
years ago on the curve-billed thrasher. I had raised a number of these
thrashers by hand, and in connection with finding out about their
tasting abilities I first fed them on the white of egg, hard-boiled and
cut into little squares. They liked it. Then I soaked more squares of
boiled egg white in evil tasting (to me) formalin. The birds came to
the dish, and also ate them. But after that for a week they refused to
eat such egg white. They had quickly learned to avoid the ill-tasting
food.
BAD-TASTING FOOD Once I hand-raised a barred owl from a nestling to
adulthood. Sometimes getting food for it was a problem, and upon
occasion I fed it frogs, which it seemed to like well enough. But then
came a day when I fed it a toad. The owl seized the toad at once.
Now toad skin, presumably as a defense weapon of the toad, secretes
a substance irritating to the mucous membranes of some animals. And
this was evidently irritating to the owl, for it did not hold the toad
long in its bill. It spat it out, and the owl's face gave evidence of
disgust. After that the owl not only refused to take toads, but it also
refused to take frogs such as it had found palatable before. Evidently
frogs looked too much like toads. The learning was effective, and
extended not only to the original object, but also to other, similar
objects.
BUCKET-DRAWING When in Florida with the Archbold Expeditions I was
studying blue jays. A very simple but amusing thing that chickadees
learn is to sit on a perch and pull up a little container of food that
dangles far below the perch on a string. Jays, along with crows, are
among the most clever of birds, as I've said before, and I gave two
jays in one cage a chance to learn the trick. In three days one of
the jays was regularly and quickly pulling up the little bucketlike
container and getting its food from it. The process was simple: the
jay reached down, seized the string in its beak, secured the slack
under its foot, and reached down again for another pull. Sometimes five
separate pulls were needed to raise the food bucket the eight inches to
the perch.
The jays were regularly fed in this manner. Soon I noticed that only
one of the two birds pulled up the bucket, though the other also fed
from it. In effect one was depending on the work of the other. After
this had gone on for a month, I wondered if the second jay, which had
never done any of the work, would be able to pull up the bucket if left
alone. Certainly it had had lots of opportunity to learn by seeing
its cage mate go through the motion. So I left it alone in the cage.
This second jay, despite its chances to learn by observation, took
one day longer to learn how to pull up the bucket of food than had
the first jay. The jays certainly learned the trick quickly through a
trial-and-error process, but simply watching the process seemed to be
of little help in learning it.
CAN BIRDS COUNT?
[Illustration]
If birds can count, it's a rather rudimentary thing--perhaps no more
than impressions of the size of groups. The widely known example
showing that birds don't seem to distinguish between one and two
persons is the ruse used by bird photographers and students of birds
who are using blinds from which to watch the birds at close range.
The hide, or blind, is a little hut built perhaps a few feet from the
nest to be photographed. If the photographer enters the blind in the
sight of the parent birds, and conceals himself there, the birds who
saw him go in will be a long time in coming to the nest and in resuming
their normal activities. But if the photographer takes a companion
with him, both go into the blind and conceal themselves, and then
one of them goes away leaving the other concealed, the bird quickly
disregards the intrusion and goes about its activities as though no one
were left in the blind. This subterfuge has long been used and is very
successful. Apparently the bird is unable to distinguish between the
two people that arrive at the nest and the one only that leaves, and
behaves as if both had gone away.
In my duck-hunting days a duck hunter who used wooden decoys told me
he was sure that there was a certain number of decoys necessary before
they were effective.
The decoys were wooden blocks, carved and painted to resemble
life-sized ducks, weighted to float like them, and anchored in shallow
water in a flock within gunshot range of the blind in which the duck
shooter sat. The idea was that ducks flying by would see the flock on
the water, assume that here was a safe resting place, and fly in and
light, or attempt to light among them, giving the wild-fowl gunner an
opportunity to shoot the wild birds.
The duck shooter claimed that if less than twenty-five or thirty decoys
were put out in the flock, the setup was much less effective than if
more than twenty-five to thirty decoys were used. He thought that the
ducks could distinguish between less than twenty-five or thirty and
more than twenty-five to thirty, and favored the latter. Though this is
distinguishing between greater and lesser amounts, it hardly comes in
the category of counting.
DISTINGUISH "MORE" FROM "LESS" However, a series of experiments
summarized on Page 121 in the periodical _Bird Banding_ for 1940 seem
to indicate that birds can distinguish between different numbers of
things, such as peas and numbers of dots. The birds, including pigeons,
parakeets, and jackdaws, were trained either to choose a certain
number of objects under certain circumstances, or to choose between
two quantities of objects with reward and punishment motivation. It
was found that these birds were able to distinguish up to a maximum
of six. That this is really counting in the human sense of the term,
which is linked with speech or written symbols, is improbable, but it
does indicate, as one would expect, that birds do at times distinguish
between different quantities, and sometimes with considerable
precision.
COURTSHIP FEEDING
[Illustration]
A young man, giving his best girl a box of chocolates, and a bird,
giving his prospective mate a worm or a berry, have this in common:
they are both practicing courtship feeding. Further, humans and birds
are the only vertebrate animals that do this.
With birds, during courtship, the female often begs to be fed by acting
like a young bird--with fluttering wings and widely gaping mouth. The
male normally places the food he has collected directly in the open
mouth of the female.
The significance of this courtship feeding has been discussed
especially by David Lack, in the scientific journal, the _Auk_. It
seems that in courtship feeding the food as such is not of primary
importance. The female does not need the food she is begging for;
indeed she may have had a full meal since her mate, whom she is
soliciting, had last eaten. Perhaps it is of help in maintaining the
bond between the pair during the period that exists before they have a
nest and young to look after. In this connection it is interesting that
with waxwings during courtship feeding the fruit that the male gives
the female may be "handed" back (by beak) and the food exchanged back
and forth.
In looking for significance and correlations in courtship feeding we
find that some species practice courtship feeding and some do not. And
the birds that do practice it are usually those in which both sexes
care for the young. It might be considered an early, useless appearance
of a habit that later becomes useful when the male feeds the incubating
female and helps feed the young.
This type of behavior, in which an act used elsewhere is introduced
into courtship, is sometimes called "symbolic." Other such symbolic
acts are the preening that sometimes takes place between a pair of
mating birds, and the passing or the manipulation of nesting material
long before there is a nest to be built.
Some species during courtship go through actions that resemble
courtship feeding except that no food is passed; the bill touching of
the mourning dove and of the waxwing falls in this category. Perhaps
it is incipient courtship feeding on its way in the long course of
evolution, either upward, to include food, or downward, away from
courtship feeding.
Their functions seem to be to give something for the pair to do;
something they can share. It helps fill up the pair's day and keep them
together. It is something that helps strengthen the bond between them,
against the day when both will be working together raising a brood.
THEY TURNED THE TABLES
[Illustration]
Most birds prey on animals enough weaker than themselves to be in no
danger from their prey; their hunting is more like that of the gunner
after rabbits than that of the hunter after lions. But there are
exceptions.
The great blue heron, armed with a spearheadlike bill, lives largely
on fish. These it spears in the water, stalking about after them on
its long legs, or waiting like a bird on a Japanese screen, as patient
as any fisherman, for its prey to come within striking distance. The
heron's size and its great bill render it safe from most enemies. But
it sometimes overestimates its ability. Audubon recorded one on the
Florida coast that, standing in deep water, up to its belly, struck a
fish too large for it. The fish dragged the bird for several yards, now
on the surface, now underwater. Finally, after a severe struggle, the
heron freed itself. It was exhausted, and stood near the shore, head
turned away from the sea. As if, Audubon said, it was afraid to make
another attempt at fish catching.
A more serious encounter for the bird was recorded in _Field and
Stream_ magazine. The heron had caught a shad about a foot long.
He tried to swallow it, but it was too big to go down. He tried to
disgorge it, but the fins of the fish, acting as barbs, kept it from
slipping backwards and out. The result was death for both bird and fish.
CAUGHT BY A CLAM The oyster catcher, a large black and white relative
of the sandpiper, feeds on, among other things, shellfish. Mussels and
oysters look like hard nuts to crack, even with a stout, wedgelike bill
such as that of the oyster catchers. The oyster catcher's favorite
feeding times are when the tide has fallen and the shellfish are
first exposed to the air and before they have closed up their shells,
and again when the tide is rising and the shells are just beginning
to open. The oyster catcher stabs into the shell, and with its bill
cuts the strong adductor muscles that hold the shells of the bivalves
together. The rest is easy. But a danger lurks here: what about
stabbing into too big a shellfish, or making an inept stab? And this
very thing has happened. On the South Carolina coast Mr. W. P. Baldwin
found a trapped, drowned bird. It was held, with the tip of its bill
caught in the shell of a hard-shell clam, as if in a trap. Apparently
the rising tide had flooded and drowned the bird.
The raven eats most anything, living or dead, and except for man
has little to fear in the northern forests where it lives. Yet from
Wisconsin comes a record of one that met his death through a porcupine.
The porcupine's quills are a dreadfully prickly covering that one
would think would protect it from most encounters. Yet one animal, the
fisher, kills and eats it as a matter of course, and wolves and bears
sometimes eat them without too many ill-effects from the spines. The
slow-moving porcupine has little regard for automobiles, and many are
run over on country roads. A porcupine is too big and tough for a raven
to kill and the Wisconsin raven had probably fed on a dead porcupine.
Stuck through its gizzard was a quill, and another, which had
apparently caused its death, was stuck in its heart, having apparently
worked there from the digestive tract.
Many small insectivorous birds eat spiders as well as insects. This
they do almost with impunity in temperate latitudes, where only
occasionally do spiders make webs strong enough to trap a bird. But
in the tropics, where there are more large spiders, their webs must
be a greater hazard to birds. That the hazard exists in both climes,
however, is shown by a goldfinch reported caught in a spider's web in
Cape Cod, Massachusetts, and a dusky flycatcher caught in a spider's
web in Cameroons, West Africa.
SURVIVAL OF THE UNFIT
[Illustration]
To care for the weak, the unfit, and the cripple is usually considered
an extremely highly developed altruism in our society. As our society
progresses, more and more provisions are made for the unfit.
In nature the unfit usually is soon weeded out. If an animal is
unable to feed itself it is doomed; or if it is less successful than
its fellows it has less chance of leaving progeny. That is natural
selection.
Hence on both counts it comes as a surprise to find two
well-authenticated cases of crippled birds, unable to search for food
for themselves, surviving for long periods.
The first is T. R. Peale's record in 1848 of a brown booby on Enderby
Island in the Pacific. An adult bird whose plumage indicated it was
several years old was found on the island, and it had only one wing,
the other having been lost by some accident and the wound completely
healed. The bird was unable to go to sea and get its own food, and was
being fed by its fellows.
The second was a frigate bird, found on the Revillagigedo Islands,
reported by A. W. Anthony in 1898. This bird, too, was fat, and had one
wing withered and useless, evidently from hatching. It had never flown.
Frigate birds are masters of the air that snatch their food on the wing
from the surface of the water, and a flightless frigate bird would be
as badly off as a flightless swallow. The cripple had been fed all its
life by its neighbors.
At first the uncritical might think, What altruism, what charity, for
the healthy to feed these two cripples. But an explanation involving
less advanced principles, principles more in keeping with what we know
about bird behavior, is possible. Remember that young birds that are
unable to begin feeding themselves at the proper time may continue to
beg for food, and be dependent for a long time, as I have shown with
young shrikes under the chapter, "Conditioning in Birds." Remember that
a young bird begging for food may be fed by adults, not its parents,
and even by other young birds (shown in "Bird Helpers at Nesting
Time"); and we have the clue.
The cripples, hungry, begged for food; the healthy birds responded by
feeding, as they might do to other begging young, and owing to the
unusual circumstances both were continued.
These certainly are cases where the unfit survived. Natural selection
has not operated. But such cases are rare exceptions.
DUST AND SNOW BATHING
[Illustration]
The taxidermist preparing a bird specimen for the museum sometimes has
to deal with one whose plumage is soiled or stained. He may have to
wash it with water. Then, to dry the plumage, fluff it, and help in
arranging the plumage so it will lie smooth and natural, he may use a
powder: corn meal, sawdust, plaster, or plaster and potato starch may
be worked into the feathers, then dusted out again. It is interesting
that birds themselves use and have used long before taxidermists a
similar method of using dust in dressing their feathers, a fact that
anyone who has watched domestic hens for any length of time must be
aware.
A DIRTY BATH Recently I watched a house sparrow dusting by the railway
track in the city of Chicago. The dust may have been in part "clean"
earth, but in part it was soot, city dust, and soft-coal debris. The
sparrows here were dingy, all had their plumage heavily impregnated
with city grime, and looked very different from the sparrows in the
country. And this sparrow I was watching when it had finished dusting
was the worst of the lot. These city sparrows, even when they bathe in
water, seem never to get much of the grime out of their feathers.
This reminded me that Oscar Heinroth once wrote that birds do not bathe
to get themselves clean, but bathe as an aid in bringing their feathers
into order and making them lie smoothly. Perhaps he is right. Certainly
my sparrow did nothing to clean himself.
It is in arid countries, plains and deserts especially, where many of
the birds take only dust baths. In more humid regions water bathing
is the rule. But some birds do both, like our flicker and our house
sparrow, bathing now in water, now in sand.
In northern climates, when the land is held in the grip of winter,
the water frozen over, and the earth covered with snow, neither dust
nor water bathing is possible. Then, it has been recorded, some birds
find a substitute in snow. Among other cases, in Alaska the hawk owl
has been seen to perch in the snow on the tops of telephone poles,
and go through the motions of bathing; in England a rook was recorded
as bathing "in crisp powdery snow as if it were taking a bath in dust
or water"; and in New England in midwinter juncos have been recorded
bathing "in light dry snow, just as other sparrows take dust baths in
hot weather."
The snow evidently is used as a substitute for dust in these northern
latitudes.
DECORATION IN THE HOME
[Illustration]
To use a bunch of flowers or a spray of leaves in decorating a room
in a house is a refinement of civilization. As the flowers fade, or
the leaves wilt, they are replaced with fresh ones. Sometimes a winter
bouquet is used that will serve for months.
There are several birds that habitually deck their nests with green
vegetation, and when it is wilted, it is renewed with fresh. The reason
is not clear. It has been suggested it is to supply humidity and, by
evaporation, coolness; it has also been suggested that its use serves a
sanitary purpose. But whatever the reason in birds' eyes, it looks like
decoration to human eyes.
This habit is common with a number of different hawks: for example,
the red-tailed hawk is reported sometimes to have its nest, a bulky
flat, basin-shaped structure in the crotch of a tree, "profusely and
beautifully lined with fresh green sprigs of white pine, which are
frequently renewed during incubation and during the earlier stages in
the growth of the young." The golden eagle is said to add green grass,
or green leaves often attached to the twigs from time to time to the
lining of the nest, especially after the young are hatched; and the
broad-winged hawk is said to add green leaves to the lining of its
nest. In quite another group of birds the same thing also occurs. A
carrion crow's nest in England was visited periodically from March to
August. Strangely no eggs were laid during this whole period, but the
birds remained in attendance. When found, fresh sprigs of oak leaves
were interwoven around the rim of the nest. On subsequent visits the
oak leaves were found to have been replaced with fresh ones, and the
leaves were kept fresh until late August.
The purple martin supplies another example. The nest boxes we put up
for them supply their main breeding places in some areas. "The parents
have a habit of collecting many green leaves and placing them in the
nest, a practice which may tend by evaporation to reduce the heat" in
the next box. "Where large colonies are breeding they sometimes injure
pear trees by stripping certain branches of their leaves," according to
E. H. Forbush.
A Madagascar weaverbird provides an example of decorating the nest
entrance of a quite different type of nest; in this case the nest is in
the shape of an inverted retort, with the entrance through the spout.
The entrance is decorated with green grass heads or with green leaves,
and the males keep adding fresh green decorations even when the eggs
are being incubated by the female.
It seems hard to believe that this is really decoration, that it is not
for some purpose--either connected with the raising of the young, or
more probably a leisure or substitute activity--something to keep the
bird busy and strengthen the bond between bird and nest when it is not
otherwise directly occupied with nesting activities.
CURIOSITY IN BIRDS
[Illustration]
Being unable to ask birds questions that will receive answers, we
have to judge their motives from appearances. And from the way some
birds act curiosity seems a strong motivation at times. They show a
disposition to inquire into things, especially strange things.
Young blue jays that I've raised and studied are among the most prying,
investigating, inquisitive birds I've known. When well fed they devoted
much time to examining things. Humans, of course, would examine objects
by picking them up in their hands, looking at and feeling them, perhaps
tasting them. The jays, with more limited equipment, would examine them
with bill and eye. When the jays were very young their toes interested
them. They pecked at and twisted their own and their neighbor's toes.
Pencils and crayons on my desk appeared to interest them particularly.
These they were continually pulling about and pecking at. They went
about picking at lines on paper, knotholes in the walls of their
cage, the red letters printed on a bottle label, and the buttons on
our clothes. Cigarettes they liked to investigate by pulling them to
pieces. It looked as if the jays were interested in finding out about
the things around them by touch and taste as much as they could.
LURED INTO DANGER Compared with jays, ducks seem rather stolid
creatures, but they have curiosity too. This was well known to the
old-time duck hunters who capitalized on it in duck shooting. The
technique is known as "tolling" and I've used two variations of it in
museum collecting.
Once on a little mountain lake in New Guinea I found a pair of ducks of
a rare species I especially needed for our collection. I stalked them
to the farthest bit of cover I could reach, a tussock of grass on the
lake margin, behind which I lay concealed. But the ducks were still too
far away for me to reach, and their feeding did not seem to be drawing
them nearer. I remembered the gunners' trick of tolling, and tried it.
I took out my white handkerchief, held it above the tussock of grass
while I kept well hidden, and waved the handkerchief back and forth.
The response was surprisingly prompt and gratifying. The two ducks
turned at once and swam right in to me so that I secured them without
any trouble.
Once on a lake in central New York State there was a flock of scaup
ducks swimming well offshore. It looked as if they never would come in
near the bank. Quite by accident a setter dog that accompanied us began
to cavort along the beach. Again the ducks turned and the whole flock
came swimming in. Only then did I remember that among old-time gunners
there was the practice of using a dog thus, a dog that was even trained
for the purpose, to jump high and run about very conspicuously while
the ducks were far out, and as the ducks came swimming in, to keep
lower and frisk about partly concealed so that the ducks would have to
come close to satisfy their curiosity.
REFERENCES
Is it true? Did it really happen? The implications and correlations are
my own, and some of the accounts on the previous pages are based on my
experiences. But many of the facts come from the writings of others.
Where the incidents are well known no documentation is given. But when
the behavior described is little known or only recently discovered
I've given a reference so that the source can be consulted. These are
arranged under the appropriate chapter headings.
BIRDS USING TOOLS
Edna Fisher, _Jour. Mammalogy_, Vol. 20, p. 21 (sea otter). P.
A. Gilbert, 1939, _Emu_, Vol. 39, pp. 18-22 (satin bower bird).
D. Lack, 1947, _Darwin's Finches_, p. 59 (woodpecker finch). D.
Morris, 1954, _British Birds_, Vol. 47, p. 33 (song thrush). A. C.
Bent, 1921, _U. S. Natl. Mus. Bull._ 113, p. 111 (gull and crow).
BIRDS AS BRIGANDS
A. L. Rand, 1954, _Fieldiana-Zoology_ (Chicago), Vol. 36, p. 35
(eagle, skua, frigate bird).
BIRDS BATHING
F. N. Bassett, 1922, _Condor_, Vol. 24, p. 63 (hummingbirds). A. C.
Bent, 1937, _U. S. Natl. Mus. Bull._, 167, p. 370 (osprey).
HOW BIRDS ANOINT THEIR FEATHERS
W. L. McAtee, 1938, _Auk_, Vol. 55, p. 98 (review).
TRAVELING BIRDS' NESTS
H. S. Swarth, 1935, _Condor_, Vol. 37, p. 84 (barn swallows). M. A.
Common, 1942, _Auk_, Vol. 59, p. 43 (tree swallow). D. L. Serventy
and H. M. Whittell, 1948, _Birds of Western Australia_, p. 243
(welcome swallow).
MALADAPTATION IN BIRDS
J. Grinnell, 1926, _Condor_, Vol. 28, p. 97 (robin). W. H.
Bergtold, 1930, _Auk_, Vol. 47, p. 571 (robin). H. W. Henshaw,
1921, _Condor_, Vol. 23, p. 109 (California woodpecker). D.
Bannerman, 1933, _Birds Tropical West Africa_, Vol. 3, p. 415
(thick-billed honey-guide).
FEATHERED BABY SITTERS AND CO-OP NURSERY NESTS
D. Davis, 1940, _Auk_, Vol. 57, p. 179 (ani). A. C. Bent, 1925, _U.
S. Natl. Mus. Bull._, 130, p. 85 (eider duck). R. C. Murphy, 1936,
_Oceanic Birds of South America_, Vol. 1, p. 398 (penguins).
BIRDS' NESTS AND THEIR SOUP
Gibson-Hill, 1948, _Malay. Nat. Jour._, Vol. 3, p. 190; F. H.
Giles, 1935, _Jour. Siam Soc. Nat. Hist. Suppl._, Vol. 10, p. 137;
and Jabouille, 1931, _L'Oiseau et Rev. Franc. d'Ornith._, Vol. 1,
n.s., p. 219 (swiftlets).
WALLED WIVES OF HORNBILLS
R. E. Moreau, 1937, _Proc. Zool. Soc._ London, 1937, p. 331
(hornbills).
BURIED EGGS AND YOUNG
A. Newton, 1893, _Dictionary of Birds_, p. 733; and D. Bannerman,
1931, _Birds Trop. West Africa_, Vol. II, p. 205 (crocodile bird).
Deusing, 1939, _Auk_, Vol. 56, p. 367 (grebe). Bent, 1925, _U. S.
Natl. Mus. Bull._, 130, p. 98 (eider duck).
THE SNOWY OWL AS A TRADE INDEX
A. Gavin, 1947, _Wilson Bull._, Vol. 59, p. 202 (snowy owl).
MONKEY BIRDS
A. L. Rand, 1954, _Fieldiana-Zoology_ (Chicago), Vol. 36, p. 23
(various "monkey-birds").
BIRD-MADE INCUBATORS
C. G. Sibley, 1946, _Condor_, Vol. 48, p. 92; Coles, 1937, _Proc.
Zool. Soc. London_, 1937, pp. 261-73; Fleay, 1937, _Emu_, Vol. 36,
pp. 153-63 (mound builders).
CORMORANT FISHING
B. Laufer, 1931, _Publ. Field Mus. Nat. Hist. (Anthr. Ser.)_, 18,
pp. 201-62; Gudger, 1926, Amer. Nat., 60, p. 5 (cormorant fishing).
THE SHRIKE'S LARDER
A. C. Bent, 1950, _U. S. Natl. Mus. Bull._ 197, p. 120 (shrike's
larder).
BIRD FLAVORS
H. B. Cott, 1946, _Proc. Zool. Soc. London_, Vol. 116, pp. 371-524
(bird flavors).
HOW MANY FEATHERS HAS A BIRD?
A. Wetmore, 1936, _Auk_, Vol. 53, p. 159; F. B. Hutt and L. Ball,
1938, _Auk_, 55, p. 651 (number of feathers).
LAST YEAR'S BIRDS' NESTS
A. C. Bent, 1925, _U. S. Natl. Mus. Bull._ 130, pp. 91, 92; H. F.
Lewis, 1938, _Bird-Lore_, Vol. 40, p. 239 (eider down).
SYMBIOSIS--ANIMALS LIVING IN MIXED HOUSEHOLDS
A. C. Bent, 1938, _U. S. Natl. Mus. Bull._ 170, pp. 384-86, 398
(burrowing owl). H. Friedmann, 1930, _Natural History_, Vol. 30, p.
205 (social weaver). W. H. Hudson, 1920, _Birds of La Plata_, Vol.
2, p. 31 (monk parrot). W. R. B. Oliver, 1930, New Zealand Birds,
p. 118 (_Sphenodon_).
BIRD APARTMENT HOUSES
A. C. Bent, 1942, _U. S. Natl. Mus. Bull._ 179, p. 490 (purple
martin). A. Wetmore and F. C. Lincoln, 1933, _Proc. U. S. Nat.
Mus._, Vol. 82, art. 25, p. 44 (West Indian woodpecker). D.
Bannerman, 1933, _Birds of Tropical West Africa_, Vol. 3, p.
381 (barbets). J. T. Emlen, 1954, _Auk_, Vol. 71, p. 16 (cliff
swallows). W. H. Hudson, 1920, _Birds of La Plata_, Vol. 2, p.
31 (monk parrot). A. Wetmore and B. H. Swales, _U. S. Natl. Mus.
Bull._ 155, p. 346 (palm chat); H. Friedmann, 1930, _Nat. Hist._,
Vol. 30, p. 205 (social weaver).
BIRD HELPERS AT NESTING TIME
A. Skutch, 1935, _Auk_, 52, p. 257 (helpers at nest). M. M. Nice,
1943, _Trans. Linn. Soc._, Vol. 6, p. 79 (young feeding young). R.
C. Murphy, 1936, _Oceanic Birds of South America_, Vol. 1, p. 360
(emperor penguins).
WEAVERS AND TAILORS IN THE BIRD WORLD
H. Friedmann, 1922, _Zoologica_, Vol. 2, p. 355 (weaverbird). C. A.
Wood, 1926, _Smithsonian Rept._, p. 349 (tailorbird).
SOCIAL PARASITES AMONG BIRDS
A. H. Miller, 1946, _Sci. Monthly_, Vol. 62, p. 238 (social
parasites).
FISH EATS BIRD!
W. E. Glegg, 1945, _Ibis_, p. 422 (fish eating birds).
CROWS ARE SMARTER THAN "WISE" OWLS
A. L. Rand, 1943, _Canad. Field Nat._, Vol. 57, p. 35 (saw-whet
owl). A. L. Rand, 1942, _Bull. Amer. Mus. Nat. Hist._, 79, p. 518
(blue jay). A. C. Bent, 1946, _U. S. Natl. Mus. Bull._ 191, p. 196
(raven), p. 266 (crow).
TAME WILD BIRDS
D. Lack, 1942, _Ibis_, p. 271 (flycatcher). A. H. Chisholm, 1943,
_Ibis_, p. 105 (honey eaters). H. H. Brimley, 1934, _Auk_, 51, p.
237 (phoebe).
BIRDS AS PILFERERS
A. L. Rand, 1954, _Fieldiana-Zoology_, Vol. 36, p. 31 (pilfering,
several species).
HIBERNATION IN BIRDS
W. L. McAtee, 1947, _Amer. Midland. Nat._, 38, p. 191 (old records
on torpidity). E. C. Jaeger, 1949, _Condor_, 51, p. 105 (poor-will).
SNAKESKINS IN BIRDS' NESTS
A. L. Rand, 1953, _Nat. Hist. Miscl._ (Chicago), No. 125
(snakeskins in nests).
CO-OPERATION BY BIRDS
A. L. Rand, 1954, _Fieldiana-Zool._ (Chicago), Vol. 36, pp. 10, 12
(co-operation, various species).
WATCHDOGS AT THE NEST
R. E. Moreau, 1942, _Ibis_, p. 240 (in Africa). D. R. Dickey and A.
J. van Rossem, 1938, _Publ. Field Mus. Nat. Hist._, _Zool. Ser._,
Vol. 23, p. 360 (in El Salvador).
BIRD GUIDES TO HONEY
H. Friedmann, 1954, _Nat. Geog. Mag._, Vol. 105, p. 551
(honey-guides).
OXPECKERS
D. Bannerman, 1948, _Birds of Tropical West Africa_, Vol. 6, p. 105
(oxpecker).
WINGS IN FEEDING
J. Delacour, 1946, _Auk_, Vol. 63, p. 441 (black heron).
CONDITIONING IN BIRDS
A. L. Rand, 1942, _Bull. Amer. Mus. Nat. Hist._, Vol. 79, p. 517
(shrikes).
POISONOUS BIRDS
E. H. Forbush, 1927, _Birds of Mass._, etc., Vol. 2, p. 34 (ruffed
grouse). D. L. Serventy and H. M. Whittell, 1948, _Birds of Western
Australia_, pp. 73, 74 (Australian pigeons). R. Meinertzhagen,
1912, _Ibis_, p. 96 (Mauritius pigeon).
BIRDS WASHING FOOD
F. G. Evenden, 1943, _Condor_, 45, p. 120 (dipper). For divers
records of washing food see _British Birds_ for 1946, 6 and 8.
HOW BIRDS USE COWS AS HUNTING DOGS
A. L. Rand, 1953, _Auk_, 70, p. 26 (ani).
BATTLE OF THE SEXES AND ITS EVOLUTIONARY SIGNIFICANCE
A. L. Rand, 1952, _Fieldiana-Zoology_ (Chicago), Vol. 34, p. 65.
WATER IN THE DESERT
C. T. Vorhies, 1945, _Univ. Ariz. Agri. Exp. Sta. Tech. Bull._ 107
(water need in desert). J. T. Emlen, Jr., and B. Blading, 1945,
_Univ. Calif. Coll. Agri. Bull._ 695, p. 34 (valley quail). E. G.
B. Meade-Waldo, 1922, _Bull. Brit. Orn. Cl._, Vol. 42, p. 69 (sand
grouse).
BIRD GRAVEYARDS
R. C. Murphy, 1936, _Oceanic Birds of South America_, Vol. 1, p.
372 (penguins). U. M. Grigg, 1950, Brit. Birds, Vol. 43, pp. 11-13
(graveyard in hollow tree). G. Simmons, 1927, _Nat. Geog. Mag._,
Vol. 52, p. 27 (petrel bones on Cima).
ANIMAL GARDENS
R. C. Murphy, 1936, _Oceanic Birds of South America_, Vol. 1, p.
374 (penguins). F. Harper, 1953, _Amer. Midland Nat._, Vol. 49, p.
6 (birds and lichens). H. W. Feilden, 1877, _Zoologist_, Vol. 1, p.
319 (arctic-fox gardens).
DROPPING THINGS
M. E. W. North, 1948, _Ibis_, p. 138-41 (lammergeier). E. Jaeger,
1951, _Condor_, 53, p. 207 (sparrow).
LEARNING BY BIRDS
A. L. Rand, 1941, _Bull. Amer. Mus. Nat. Hist._, Vol. 78, p. 222
(thrasher). A. L. Rand, 1942, _Bull. Amer. Mus. Nat. Hist._, Vol.
79, p. 518 (blue jay).
CAN BIRDS COUNT?
_Bird-banding_, 1940, Vol. 11, p. 121 (summary various experiments).
COURTSHIP FEEDING
D. Lack, 1940, _Auk_, Vol. 57, p. 169 (courtship feeding).
THEY TURNED THE TABLES
A. C. Bent, 1926, _U. S. Natl. Mus. Bull._ 135, p. 109 (great
blue heron). W. P. Baldwin, 1946, _Auk_, Vol. 63, p. 589 (oyster
catcher). G. Mackay, 1929, _Auk_, 46, p. 123 (goldfinch). D.
Bannerman, 1936, _Birds Tropical West Africa_, Vol. 4, p. 244
(dusky flycatcher).
SURVIVAL OF THE UNFIT
A. W. Anthony, 1898, _Auk_, Vol. 15, p. 314 (frigate bird). J.
Cassin, 1858, _United States exploring expedition ..., Mammals
and Birds_, Philadelphia, p. 364 (brown booby).
DECORATION IN THE HOME
A. C. Bent, 1937, _U. S. Nat. Mus. Bull._ 167, p. 151 (red-tailed
hawk), p. 296 (golden eagle). M. R. Lieff and N. P. Jordan, 1950,
_British Birds_, Vol. 43, p. 56 (carrion crow). E. H. Forbush,
1929, _Birds of Mass., etc._, Vol. 3, p. 141 (purple martin). A. L.
Rand, 1936, _Bull. Amer. Mus. Nat. Hist._, Vol. 72, pp. 487, 490
(weaverbird).
INDEX
adaptation, 31
Aeschylus, death of, 186
Aeschylus on vultures, 172
ani, feeding rates of, 168
anointing feathers, 25
anting, 27
anvil, thrush's, 15
apartment houses, 77
Arctic fox and snowy owl, 49
association of: burrowing owl, prairie dog, snake, 73
lizard, petrel, 75
parrot, duck, opossum, 75
social weaver, falcon, 74
baby sitters, 35
bad and good birds, 152
bathing in dust, 204
bathing in snow, 204
bathing in water, 22, 205
beehives, guiding to, 125
beeswax as bird food, 125
bird of paradise, 162
boat names, 84
booming of nighthawk, 135
bower, painting of, 16
brigands, birds as, 19
brush turkey, 54
bucket drawing by jay, 190
buried eggs, 45
buried young, 45
cassowaries swim, 149
cattle disease and oxpeckers, 129
_Chicago Tribune_ farm, 151
cliff dwellers, 78
colony, mixed, 73
colony nesters, 77
color, change in jay, 164
color and palatability, 63
communistic care of young, 37
community nests, 35
conditioning, 136
conservation, 151
co-operation, 117
co-operation: birds and monkeys, 51-53
cow and ani, 167
in carrying prey, 118
in fishing by pelican, 118
in killing skunk, 119
co-op nursery, 35
cormorant: fishing with, 57
training, 58
cosmetics, various, 26
counting, of photographers, 193
distinguishing more from less, 193
courtship feeding, 195
function of, 197
significance of, 195
covering eggs: by eider duck, 47
by grebe, 47
cows, use as hunting dogs, 167
credit and snowy owl, 48
cripples, cared for, 201
crocodile bird, 45
crow, intelligence of, 98
crows profit by experience, 99
curiosity, 210
dangerous prey, 198
death: caused by clam, 199
by porcupine, 202
by spiders, 200
decoration: function of, 209
in nests, 207
snakeskin in, 113
droppings things: 186
by crows, 16
by gulls, 16, 187
by lammergeier, 186
by sparrow, 187
reason for, 188
drumming: of grouse, 134
of woodpecker, 133
drunkenness, 32
duck, muscovy, 162
ecological competition, 173
eggs: buried, 55
covered, 46, 47
in other birds' nests, 91
specializations, 93
eider down, 71
environment modifies heredity, 139
Eskimo, credit to, 48
experience: crows profit by, 99
learning by, 189
feathers: and size of bird, 67
and temperature, 67
number of, 66
feeding rates of ani, 168
fish eats bird, 95
fishing with cormorants, 57
flavor of flesh, 63, 142
flesh: flavor of, 63, 142
poisonous, 141
fluctuations in the Arctic, 48
food: impaling of by shrike, 61
storage of, 32, 61
foster parents, 93
foster young, specialization in, 93
foxing, 166
frogs mistaken for birds, 109
gardens: animal, 183
ecological balance in, 153
of Arctic fox, 185
good and bad birds, 152
grackles, character of, 152
graveyards: 180
in hollow tree, 181
on island, 182
penguins', 180
green hunting jay, 164
guarding birds' nests, by insects, 121
guides to honey, 124
hair pulling, 102
helpers at nesting time, 81
heredity modified by environment, 139
hibernation, 108
honey guides: 124
lead to big game, 125
hornbills' nests, 42
households, mixed, 73
identification: caution in making, 161
errors in, 161
over the telephone, 160
sight, 161
incubation, artificial, 56
incubators, bird-made, 54
infantile behavior modified, 137
inquisitive birds, 210
instrumental music, 133
intelligence, comparative, 98
intoxication, 32
jays: change of color in, 164
helping at nest, 81
kingfisher: a painting of, 143
classical allusions to, 145
on the telephone, 143
variation in, 144
lammergeier and Aeschylus, 186
larder, shrike's, 60
laughing jackass, voice of, 145
learning, 189
lemming and Arctic fox, 49
lichens and birds, 184
listing of birds, early, 171
maladaptation, 31
megapode nesting, 54
migration, 28
mixed households, 73
monkey birds: 51
and birds, various, 52-53
mound builder and nest, 54
music, instrumental, 133
names: appropriateness, 51, 85
available scientific, 85
domestic and foreign, 157
euphony needed, 84
for boats, 84
how given, 51
natural selection not operating, 203
nests: co-operative, 79
decoration of, 207
Guarded by insects, 121
helpers at, 81
in soup, 38, 48
last year's, 69
leaves in, 207
megapodes, 54
parasitism, 91
secondhand, 69
subleases on, 69
transportation of, 28
use by man, 71
use of snakeskin in, 111
walled, of hornbill, 42--44
nest building, co-operative, 79
nidification, reptile type, 56
nursery, 35
oil glands, 25
owl, and toad, 190
owl, intelligence of, 98
oxpecker: 127
value to herds, 128
painting a kingfisher, 143
painting of bower, 16
palatability, 63
penguins, maternal, 36
people, birds perching on, 102
pilfering: 104
by grackle, 106
by kingfisher, 105
by shrike, 105
by starling, 105
poison fruit, 31
poisonous birds, 140
poor-will in hibernation, 109
powder down, 26
preening, 25
probe, used by finch, 17
references, 213
retarded development, 137
rhino bird, 128
robbery: by birds, 19,104
by eagle, 19, 20
by frigate bird, 20
by raven, 99
by skua, 21
Rome, founding of, 171
Romulus and Remus as bird watchers, 171
Salvador bird voices, 157
sand grouse carrying water, 178
sea serpents: identification of, 147
in Kenya, 148
in New Guinea, 148
sentinel of the monkey, 53
sewing nests, 89
sexes: battle of, 173
different diets of, 175
sexual differences, ecological significance of, 173
shrike's larder, 60
shrike, young, infantile behavior prolonged, 137
slave of the monkeys, 52
snails, broken on anvil, 15
snakeskins: in nests, 111
as decorations, 112
bibliographic work on use of, 114
reasons for using, 115
theories of use, 113
snowy owl, as trade index, 49
social parasites, 33, 91
soothsayers use birds, 172
sounds produced mechanically, 134
soup, birds'-nest, 38
storage: of acorns, 32
of fish, 33
survival of unfit, 201
swifts' nests, 38-41
symbiosis, 73
tables turned, 198
tailorbirds, 89
tameness, 101
taste in birds, 189
telephone: conversations on, 143, 151
identification over, 160
theft, petty, 104
thrush, breaking snail's shell, 15
tick bird, 128
ticks, food of oxpecker, 128
tolling of ducks, 211
tool, use of, 15
torpidity, 108
trade index, snowy owls as, 49
unfit survive, 201
vegetation and penguins, 183
washing food: 154
reasons for, 156
watchdogs at nests, 121
water: carried by birds, 46, 178
flights to, 178
need of, 177
weaving nests, 88
wing music of owl, 134
wings: use of, 130
in feeding, 131
winnowing of snipe, 134
wisdom, owl, symbol of, 98
young: buried, 45
communistic care of, 37
fed by other young, 81, 203
honey-guide's, 33
independent from hatching, 55
* * * * *
Transcriber Note
Minor typos corrected.
*** End of this LibraryBlog Digital Book "Stray Feathers From a Bird Man's Desk" ***
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