At the best we can only guess at the motives of the birds and beasts. As I have elsewhere said, they nearly all have reference in some way to the self-preservation of these creatures. But how the bits of an old snake-skin in a bird's nest can contribute specially to this end, I cannot see.
Nature is not always consistent; she does not always choose the best means to a given end. For instance, all the wrens except our house wren seem to use about the best material at hand for their nests. What can be more unsuitable, untractable, for a nest in a hole or cavity than the twigs the house wren uses? Dry grasses or bits of soft bark would bend and adapt themselves easily to the exigencies of the case; but stiff, unyielding twigs! What a contrast to the suitableness of the material the hummingbird uses – the down of some plant, which seems to have a poetic fitness!
Yesterday in my walk I saw where a red squirrel had stripped the soft outer bark off a group of red cedars to build its winter's nest with. This also seemed fit, – fit that such a creature of the trees should not go to the ground for its nest-material, and should choose something soft and pliable. Among the birches, it probably gathers the fine curling shreds of the birch bark.
Beside my path in the woods a downy woodpecker, late one fall, drilled a hole in the top of a small dead black birch for his winter quarters. My attention was first called to his doings by the white chips upon the ground. Every day as I passed I would rap upon his tree, and if he was in he would appear at his door and ask plainly enough what I wanted now. One day when I rapped, something else appeared at the door – I could not make out what. I continued my rapping, when out came two flying-squirrels. On the tree being given a vigorous shake, it broke off at the hole, and the squirrels went sliding down the air to the foot of a hemlock, up which they disappeared. They had dispossessed Downy of his house, had carried in some grass and leaves for a nest, and were as snug as a bug in a rug. Downy drilled another cell in a dead oak farther up the hill, and, I hope, passed the winter there unmolested. Such incidents, comic or tragic, as they chance to strike us, are happening all about us, if we have eyes to see them.
The next season, near sundown of a late November day, I saw Downy trying to get possession of a hole not his own. I chanced to be passing under a maple, when white chips upon the ground again caused me to scrutinize the branches overhead. Just then I saw Downy come to the tree, and, hopping around on the under side of a large dry limb, begin to make passes at something with his beak. Presently I made out a round hole there, with something in it returning Downy's thrusts. The sparring continued some moments. Downy would hop away a few feet, then return to the attack, each time to be met by the occupant of the hole. I suspected an English sparrow had taken possession of Downy's cell in his absence during the day, but I was wrong. Downy flew to another branch, and I tossed up a stone against the one that contained the hole, when, with a sharp, steely note, out came a hairy woodpecker and alighted on a near-by branch. Downy, then, had the "cheek" to try to turn his large rival out of doors – and it was Hairy's cell, too; one could see that by the size of the entrance. Thus loosely does the rule of meum and tuum obtain in the woods. There is no moral code in nature. Might reads right. Man in communities has evolved ethical standards of conduct, but nations, in their dealings with one another, are still largely in a state of savage nature, and seek to establish the right, as dogs do, by the appeal to battle.
One season a wood duck laid her eggs in a cavity in the top of a tall yellow birch near the spring that supplies my cabin with water. A bold climber "shinned" up the fifty or sixty feet of rough tree-trunk and looked in upon the eleven eggs. They were beyond the reach of his arm, in a well-like cavity over three feet deep. How would the mother duck get her young up out of that well and down to the ground? We watched, hoping to see her in the act. But we did not. She may have done it at night or very early in the morning. All we know is that when Amasa one morning passed that way, there sat eleven little tufts of black and yellow down in the spring, with the mother duck near by. It was a pretty sight. The feat of getting down from the tree-top cradle had been safely effected, probably by the young clambering up on the inside walls of the cavity and then tumbling out into the air and coming down gently like huge snowflakes. They are mostly down, and why should they not fall without any danger to life or limb? The notion that the mother duck takes the young one by one in her beak and carries them to the creek is doubtless erroneous. Mr. William Brewster once saw the golden-eye, whose habits of nesting are like those of the wood duck, get its young from the nest to the water in this manner: The mother bird alighted in the water under the nest, looked all around to see that the coast was clear, and then gave a peculiar call. Instantly the young shot out of the cavity that held them, as if the tree had taken an emetic, and came softly down to the water beside their mother. Another observer assures me that he once found a newly hatched duckling hung by the neck in the fork of a bush under a tree in which a brood of Wood ducks had been hatched.
The ways of nature, – who can map them, or fathom them, or interpret them, or do much more than read a hint correctly here and there? Of one thing we may be pretty certain, namely, that the ways of wild nature may be studied in our human ways, inasmuch as the latter are an evolution from the former, till we come to the ethical code, to altruism and self-sacrifice. Here we seem to breathe another air, though probably this code differs no more from the animal standards of conduct than our physical atmosphere differs from that of early geologic time.
Our moral code must in some way have been evolved from our rude animal instincts. It came from within; its possibilities were all in nature. If not, where were they?
I have seen disinterested acts among the birds, or what looked like such, as when one bird feeds the young of another species when it hears them crying for food. But that a bird would feed a grown bird of another species, or even of its own, to keep it from starving, I have my doubts. I am quite positive that mice will try to pull one of their fellows out of a trap, but what the motive is, who shall say? Would the same mice share their last crumb with their fellow if he were starving? That, of course, would be a much nearer approach to the human code, and is too much to expect. Bees will clear their fellows of honey, but whether it be to help them, or to save the honey, is a question.
In my youth I saw a parent weasel seize one of its nearly grown young which I had wounded and carry it across an open barway, in spite of my efforts to hinder it. A friend of mine, who is a careful observer, says he once wounded a shrike so that it fell to the ground, but before he got to it, it recovered itself and flew with difficulty toward some near trees, calling to its mate the while; the mate came and seemed to get beneath the wounded bird and buoy it up, so aiding it that it gained the top of a tall tree, where my friend left it. But in neither instance can we call this helpfulness entirely disinterested, or pure altruism.
Emerson said that he was an endless experimenter with no past at his back. This is just what Nature is. She experiments endlessly, seeking new ways, new modes, new forms, and is ever intent upon breaking away from the past. In this way, as Darwin showed, she attains to new species. She is blind, she gropes her way, she trusts to luck; all her successes are chance hits. Whenever I look over my right shoulder, as I sit at my desk writing these sentences, I see a long shoot of a honeysuckle that came in through a crack of my imperfectly closed window last summer. It came in looking, or rather feeling, for something to cling to. It first dropped down upon a pile of books, then reached off till it struck the window-sill of another large window; along this it crept, its regular leaves standing up like so many pairs of green ears,