A strange thing about the perching toes is the way they are made to hold on, so that the birds can sleep on a perch, and not fall. Inside the toes are tendons, something like cords, which act like elastic rubber. When a bird bends his leg, the toes are drawn up and held so. When he is sitting on a perch, he could not fall off if he wanted to.
Birds who have the "scratching foot," the second kind, mostly go about on the ground, or wade in the water. They do not usually sleep on perches, but sleep standing, or crouch on the ground. In the arctic regions, where there is a great deal of snow, some birds with scratching feet, who have to go about in it, have in winter what has been called "snowshoes," because it enables them to walk on the snow with ease. It is a web-like growth on the side of each toe, which serves the same purpose with birds that snowshoes do with men, keeps them from sinking into the snow.
Birds who have the "swimming foot," the third kind, have the toes made into a paddle by webs stretched between them. They are the water birds,—ducks, geese, gulls, and others.
The toes of all birds have long, sharp claws, not at all like our toe-nails. In the whip-poor-will and the nighthawk, one edge of the middle claw has teeth like a comb.
The long slim part above the toes, what we call the leg, is named in the books the "tarsus." The tarsus is generally bare, with a leathery skin; but in some hawks and owls it is covered with feathers. Birds who live away up in the cold have feathers down on to the toes.
On looking carefully at one of these bare legs, it will be seen that it is not smooth like a lead pencil. It is marked in a sort of pattern. Different species of birds show different patterns. Some look like the shingles on a roof; others like little squares or plates; and some are finer, like scales on a tiny fish.
These marks help in arranging birds in the books. That is, all who have the same pattern are said to be related.
The legs of birds are not all of the same length for their size. Some who never go about on the ground, like hummingbirds, swallows, and swifts, have very short legs. Birds who walk and hop on the ground have them longer, and birds who wade in the water have the longest of all.