Ways of Nature

by John Burroughs

How far the different species of song-birds acquire each their peculiar songs by imitation is a question that has not yet been fully settled. That imitation has much to do with it admits of little doubt. The song of a bird is of secondary importance in its life. Birds reared in captivity, where they have never heard the songs of their kind, sing at the proper age, but not always the songs of their parents. Mr. Scott of Princeton proved this with his orioles. They sang at the proper age, but not the regular oriole song. I am told that there is a well-authenticated case of an English sparrow brought up with canaries that learned to sing like a canary. "The Hon. Daines Barrington placed three young linnets with three different foster-parents, the skylark, the woodlark, and the titlark or meadow-pipit, and each adopted, through imitation, the song of its foster-parent." I have myself heard goldfinches that were reared in a cage sing beautifully, but not the regular goldfinch song; it was clearly the song of a finch, but of what finch I could not have told. I have also heard a robin that sang to perfection the song of the brown thrasher; it had, no doubt, caught it by imitation. I have heard another robin that had the call of the quail interpolated into its own proper robin's song. But I have yet to hear of a robin building a nest like a brown thrasher, or of an oriole building a nest like a robin, or of kingfishers drilling for grubs in a tree. The hen cannot keep out of the water the ducks she has hatched, nor can the duck coax into the water the chickens she has hatched. The cowbird hatched and reared by the sparrow, or the warbler, or the vireo does not sing the song of the foster-parent. Why? Did its parent not try to teach it? I have no evidence that young birds sing, except occasionally in a low, tentative kind of way, till they return the following season, and then birds of a feather flock together, robins staying with robins, and cowbirds with cowbirds, each singing the song of its species. The songs of bobolinks differ in different localities, but those of the same locality always sing alike. I once had a caged skylark that imitated the songs of nearly every bird in my neighborhood.

Mr. Leander S. Keyser, author of "Birds of the Rockies," relates in "Forest and Stream" the results of his experiments with a variety of birds taken from the nest while very young and reared in captivity; among them meadowlarks, red-winged blackbirds, brown thrashers, blue jays, wood thrushes, catbirds, flickers, woodpeckers, and several others. Did they receive any parental instruction? Not a bit of it, and yet at the proper age they flew, perched, called, and sang like their wild fellows—all except the robins and the red-winged blackbirds: these did not sing the songs of their species, but sang a medley made up of curious imitations of human and other sounds. And the blue jay never learned to sing "the sweet gurgling roulade of the wild jays," though it gave the blue jay call correctly. Mr. Keyser's experiment was interesting and valuable, but his sagacity fails him when interpreting the action of the jay in roosting in an exposed place after it had been given its liberty. He thinks this showed how little instinct can be relied on, and how much the bird needed parental instruction. Could he not see that the artificial life of the bird in the cage had demoralized its instincts, and that acquired habits had supplanted native tendencies? The bird had learned to be unafraid in the cage, and why should it be afraid out of the cage? This reminds me of a letter from a correspondent: he had a tame crow that was not afraid of a gun; therefore he concluded that the old crows must instill the fear of guns into their young! Why should the crow be afraid of a gun, if it had learned not to be afraid of the gunner?

I have seen a young chickadee fly late in the day from the nest in the cavity of a tree straight to a pear-tree, where it perched close to the trunk and remained unregarded by its parents till next morning. But no doubt its parents had given it minute directions before it left the nest how to fly and where to perch!

That animals learn by experience in a limited way is very certain. Yet that old birds build better nests or sing better than young ones it would be hard to prove, though it seems reasonable that it should be so.

Rarely does one see nests of the same species of varying degrees of excellence—that is, first nests in the spring. The second nest of any species is likely to be a more hurried and incomplete affair. Some species are at all times poor nest-builders, as the cuckoos and the pigeons. Other birds are good nest-builders, as the orioles, the thrushes, the finches, the warblers, the hummingbirds, and one never finds an inferior specimen of the nests of any of these birds. There is probably no more improvement in this respect among birds than there is among insects.

I have no proof that wild birds improve in singing. One does not hear a vireo, or a finch, or a thrush, or a warbler that is noticeably inferior as a songster to its fellows; their songs are all alike, except in the few rare cases when one hears a master songster among its kind; but whether this mastery is natural or acquired, who shall tell?

What birds learn about migration, if anything, I do not see that we have any means of finding out.

It has been observed of birds reared under artificial conditions that the young males practice a long time before they sing well. That this is true of wild birds, there is no proof. What birds and animals learn by experience is greater cunning. Does not even an old trout know more about hooks than a young one? Birds of any kind that are much hunted become wilder, even though they have not had the experience of being shot. Ask any duck or grouse or quail hunter if this is not so. Our ruffed grouse learns to fly with a corkscrew motion where it is much fired at on the wing. How wary and cautious the fox becomes in regions where it is much trapped and hunted! Even the woodchuck becomes very wild on the farms where it is much shot at, and this wildness extends to its young. In his "Wilderness Hunter" President Roosevelt says the same thing of the big game of the Rockies. Antelope and deer can be lured near the concealed hunter by the waving of a small flag till they are shot at a few times. Then they see through the trick. "The burnt child fears the fire." Animals profit by experience in this way; they learn what not to do. In the accumulation of positive knowledge, so far as we know, they make little or no progress. Birds and beasts will adapt themselves more or less to their environment, but plants and trees will do that, too. The rats in Jamaica have learned to nest in trees to escape the mongoose, but this is only the triumph of the instinct of self-preservation. The mongoose has not yet learned to climb trees; the pressure of need is not yet great enough. It is said that in districts subject to floods moor-hens often build in trees. All animals will change their habits under pressure of necessity; man changes his without this pressure. The Duke of Argyll saw a bald eagle seize a fish in the stream—an unusual proceeding; but the eagle was doubtless very hungry, and there was no osprey near upon whom to levy tribute.

Romanes found that rats would get certain semi-liquid foods out of a bottle with their tails, as a cat will get milk out of a jar with her paw, but neither ever progresses so far as to use any sort of tool for the purpose, or to tip the vessel over. Animals practice concealment to secure their prey, but not deception, as man does. They do not use lures or disguises, or traps or poison.

There is, of course, no limit to the variety and adaptiveness of nature taken as a whole, but each species is hedged about by impassable limitations. The ouzel is akin to the thrushes, and yet it lives along and in the water. Does it ever take to the fields and woods, and live on fruit and land-insects, and nest in trees like other thrushes? So with all birds and beasts. They vary constantly, but not in one lifetime, and the sum of these variations, accumulated through natural selection, as Darwin has shown, gives rise, in the course of long periods of time, to new species.