Part 5

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

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!

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

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

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

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

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.