Ways of Nature

by John Burroughs

This almost looks like a well-laid scheme on the part of the tree to defeat its enemies. But see how inevitable the whole process is. Check the direct flow of a current and it will flow out at the sides; check the side issues and they will push out on their sides, and so on. So it is with the tree or seedling. The more it is cropped, the more it branches and rebranches, pushing out laterally as its vertical growth is checked, till it has surrounded the central stalk on all sides with a dense, thorny hedge. Then as this stalk is no longer cropped, it leads the tree upward. The lateral branches are starved, and in a few years the tree stands with little or no evidence of the ordeal it has passed through. In like manner the nature of the animals prompts them to the deeds they do, and we think of them as the result of a mental process, because similar acts in ourselves are the result of such a process.

See how the mice begin to press into our buildings as the fall comes on. Do they know winter is coming? In the same way the vegetable world knows it is coming when it prepares for winter, or the insect world when it makes ready, but not as you and I know it. The woodchuck "holes up" in late September; the crows flock and select their rookery about the same time, and the small wood newts or salamanders soon begin to migrate to the marshes. They all know winter is coming, just as much as the tree knows, when in August it forms its new buds for the next year, or as the flower knows that its color and perfume will attract the insects, and no more. The general intelligence of nature settles all these and similar things.

When a bird selects a site for its nest, it seems, on first view, as if it must actually think, reflect, compare, as you and I do when we decide where to place our house. I saw a little chipping sparrow trying to decide between two raspberry bushes. She kept going from one to the other, peering, inspecting, and apparently weighing the advantages of each. I saw a robin in the woodbine on the side of the house trying to decide which particular place was the best site for her nest. She hopped to this tangle of shoots and sat down, then to that, she turned around, she readjusted herself, she looked about, she worked her feet beneath her, she was slow in making up her mind. Did she make up her mind? Did she think, compare, weigh? I do not believe it. When she found the right conditions, she no doubt felt pleasure and satisfaction, and that settled the question. An inward, instinctive want was met and satisfied by an outward material condition. In the same way the hermit crab goes from shell to shell upon the beach, seeking one to its liking. Sometimes two crabs fall to fighting over a shell that each wants. Can we believe that the hermit crab thinks and reasons? It selects the suitable shell instinctively, and not by an individual act of judgment. Instinct is not always inerrant, though it makes fewer mistakes than reason does. The red squirrel usually knows how to come at the meat in the butternut with the least gnawing, but now and then he makes a mistake and strikes the edge of the kernel, instead of the flat side. The cliff swallow will stick her mud nest under the eaves of a barn where the boards are planed so smooth that the nest sooner or later is bound to fall. She seems to have no judgment in the matter. Her ancestors built upon the face of high cliffs, where the mud adhered more firmly.

A wood thrush began a nest in one of my maples, as usual making the foundation of dry leaves, bits of paper, and dry grass. After the third day the site on the branch was bare, the wind having swept away every vestige of the nest. As I passed beneath the tree I saw the thrush standing where the nest had been, apparently in deep thought. A few days afterward I looked again, and the nest was completed. The bird had got ahead of the wind at last. The nesting-instinct had triumphed over the weather.

Take the case of the little yellow warbler when the cowbird drops her egg into its nest—does anything like a process of thought or reflection pass in the bird's mind then? The warbler is much disturbed when she discovers the strange egg, and her mate appears to share her agitation. Then after a time, and after the two have apparently considered the matter together, the mother bird proceeds to bury the egg by building another nest on top of the old one. If another cowbird's egg is dropped in this one, she will proceed to get rid of this in the same way. This all looks very like reflection. But let us consider the matter a moment. This thing between the cowbird and the warbler has been going on for innumerable generations. The yellow warbler seems to be the favorite host of this parasite, and something like a special instinct may have grown up in the warbler with reference to this strange egg. The bird reacts, as the psychologists say, at sight of it, then she proceeds to dispose of it in the way above described. All yellow warblers act in the same manner, which is the way of instinct. Now if this procedure was the result of an individual thought or calculation on the part of the birds, they would not all do the same thing; different lines of conduct would be hit upon. How much simpler and easier it would be to throw the egg out—how much more like an act of rational intelligence. So far as I know, no bird does eject this parasitical egg, and no other bird besides the yellow warbler gets rid of it in the way I have described. I have found a deserted phœbe's nest with one egg of the phœbe and one of the cowbird in it.

Some of our wild birds have changed their habits of nesting, coming from the woods and the rocks to the protection of our buildings. The phœbe-bird and the cliff swallow are marked examples. We ascribe the change to the birds' intelligence, but to my mind it shows only their natural adaptiveness. Take the cliff swallow, for instance; it has largely left the cliffs for the eaves of our buildings. How naturally and instinctively this change has come about! In an open farming country insect life is much more varied and abundant than in a wild, unsettled country. This greater food supply naturally attracts the swallows. Then the protecting eaves of the buildings would stimulate their nesting-instincts. The abundance of mud along the highways and about the farm would also no doubt have its effect, and the birds would adopt the new sites as a matter of course. Or take the phœbe, which originally built its nest under ledges, and does so still to some extent. It, too, would find a more abundant food supply in the vicinity of farm-buildings and bridges. The protected nesting-sites afforded by sheds and porches would likewise stimulate its nesting-instincts, and attract the bird as we see it attracted each spring.

Nearly everything an animal does is the result of an inborn instinct acted upon by an outward stimulus. The margin wherein intelligent choice plays a part is very small. But it does at times play a part—perceptive intelligence, but not rational intelligence. The insects do many things that look like intelligence, yet how these things differ from human intelligence may be seen in the case of one of our solitary wasps,—the mud-dauber,—which sometimes builds its cell with great labor, then seals it up without laying its egg and storing it with the accustomed spiders. Intelligence never makes that kind of a mistake, but instinct does. Instinct acts more in the invariable way of a machine. Certain of the solitary wasps bring their game—spider, or bug, or grasshopper—and place it just at the entrance of their hole, and then go into their den apparently to see that all is right before they carry it in.

Fabre, the French naturalist, experimented with one of these wasps, as follows: While the wasp was in its den he moved its grasshopper a few inches away. The wasp came out, brought it to the opening as before, and went within a second time; again the game was removed, again the wasp came out and brought it back and entered her nest as before. This little comedy was repeated over and over; each time the wasp felt compelled to enter her hole before dragging in the grasshopper. She was like a machine that would work that way and no other. Step must follow step in just such order. Any interruption of the regular method and she must begin over again. This is instinct, and the incident shows how widely it differs from conscious intelligence.

If you have a tame chipmunk, turn him loose in an empty room and give him some nuts. Finding no place to hide them, he will doubtless carry them into a corner and pretend to cover them up. You will see his paws move quickly about them for an instant as if in the act of pulling leaves or mould over them. His machine, too, must work in that way. After the nuts have been laid down, the next thing in order is to cover them, and he makes the motions all in due form. Intelligence would have omitted this useless act.

A canary-bird in its cage will go through all the motions of taking a bath in front of the cup that holds its drinking-water when it can only dip its bill into the liquid. The sight or touch of the water excites it and sets it going, and with now and then a drop thrown from its beak it will keep up the flirting and fluttering motion of its tail and wings precisely as if taking a real instead of an imaginary bath.