Part 2

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

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

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

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

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

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

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.