INSTRUMENTAL MUSIC OF BIRDS
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 [Ref]
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 [Ref]
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.