Part 2

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

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

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

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.