Some have compared the shrike's song to the creaking of a rusty gate-hinge, but it is not quite so
bad as that. Still it is unmistakably the voice of a savage. None of the birds of prey have musical voices.
The shrike had probably come to town to try his luck with English sparrows. I do not know that he caught any, but in a neighboring city I heard of a shrike that made great havoc with the sparrows.
VI
When Nature made the flying squirrel she seems to have whispered a hint or promise of the same gift to the red squirrel. At least there is a distinct suggestion of the same power in the latter. When hard pressed the red squirrel will trust himself to the air with the same faith that the flying squirrel does, but, it must be admitted, with only a fraction of the success of the latter. He makes himself into a rude sort of parachute, which breaks the force of his fall very much. The other day my dog ran one up the side of the house, through the woodbine, upon the roof. As I opened fire upon him with handfuls of gravel, to give him to understand he was not welcome there, he boldly launched out into the air and came down upon the gravel walk, thirty feet below, with surprising lightness and apparently without the least shock or injury, and was off in an instant beyond the reach of the dog. On another occasion I saw one leap from the top of a hickory-tree and fall through the air at least forty feet and alight without injury. During their descent upon such occasions their legs are widely extended, their bodies are
broadened and flattened, the tail stiffened and slightly curved, and a curious tremulous motion runs through all. It is very obvious that a deliberate attempt is made to present the broadest surface possible to the air, and I think a red squirrel might leap from almost any height to the ground without serious injury. Our flying squirrel is in no proper sense a flyer. On the ground he is more helpless than a chipmunk, because less agile. He can only sail or slide down a steep incline from the top of one tree to the foot of another. The flying squirrel is active only at night; hence its large, soft eyes, its soft fur, and its gentle, shrinking ways. It is the gentlest and most harmless of our rodents. A pair of them for two or three successive years had their nest behind the blinds of an upper window of a large, unoccupied country house near me. You could stand in the room inside and observe the happy family through the window pane against which their nest pressed. There on the window sill lay a pile of large, shining chestnuts, which they were evidently holding against a time of scarcity, as the pile did not diminish while I observed them. The nest was composed of cotton and wool which they filched from a bed in one of the chambers, and it was always a mystery how they got into the room to obtain it. There seemed to be no other avenue but the chimney flue.
There are always gradations in nature, or in natural life; no very abrupt departures. If you find any marked trait or gift in a species you will find
hints and suggestions of it, or, as it were, preliminary studies of it, in other allied species. I am not thinking of the law of evolution which binds together the animal life of the globe, but of a kind of overflow in nature which carries any marked endowment or characteristic of a species in lessened force or completion to other surrounding species. Or if looked at from the other way, a progressive series, the idea being more and more fully carried out in each succeeding type—a kind of lateral and secondary evolution. Thus there are progressive series among our song-birds. The brown thrasher is an advance upon the catbird, and the mockingbird is an advance upon the brown thrasher in the same direction. Each one carries the special gift of song or mimicking some stages forward. The same among the larks, through the so-called meadowlark and the shore lark, up to the crowning triumph of the skylark. The nightingale also finishes a series which starts with the hedge warbler and includes the robin redbreast. Our ground-sparrow songs probably reach their highest perfection in the song of the fox sparrow; our finches in that of the purple finch, etc.
The same thing may be observed in other fields. The idea of the flying fish, the fish that leaves the water and takes for a moment to the air, does not seem to have exhausted itself till we reach the walking fish of tropical America, or the tree-climbing fish of India. From the protective coloring of certain insects, animals, and birds, the step is not far to actual mimicry of certain special forms and colors.
The naturalists find in Java a spider that exactly copies upon a leaf the form and colors of bird droppings. How many studies of honey-gathering bees did nature make before she achieved her masterpiece in this line in the honey-bee of our hives? The skunk's peculiar weapon of defense is suggested by the mink and the weasel. Is not the beaver the head of the series of gnawers, the loon of divers, the condor of soarers? Always one species that goes beyond any other. Look over a collection of African animals and see how high shouldered they are, how many hints or prophecies of the giraffe there are before the giraffe is reached. After nature had made the common turtle, of course she would not stop till she had made the box tortoise. In him the idea is fully realized. On the body of the porcupine the quills are detached and stuck into the flesh of its enemy on being touched; but nature has not stopped here. With the tail the animal strikes its quills into its assailant. Now if some animal could be found that actually threw its quills, at a distance of several feet, the idea would be still further carried out.