Every one has seen a robin run over the gra.s.s and turn his head one side to listen. It is supposed that he hears the earthworm move under the sod, and if he is watched, he will often be seen to pull the worm from that very spot.

When a woodp.e.c.k.e.r taps on a tree trunk and turns his head to listen, it is thought that he hears the grub stir under the bark, for when he begins to cut the bark away, he is pretty sure to find and draw it out.

Birds that are much hunted by men, like ducks and geese, get to be very knowing, and show how wonderful is their hearing. They can tell the difference between a noise made by an animal and that made by a man. A deer or any animal may crash through the bushes, and they pay no attention to it, but if a man makes the least sound they are off in an instant.

A bird's ears are behind the eyes, and a little below them. They are covered by delicate feathers that hide them from sight. When the bird raises these feathers--perhaps to hear better--they look like tiny ear m.u.f.fs.

Owls have little flaps of skin with which they can shut up their ears when they wish to be quiet. This must be very useful to birds who prefer to sleep during the day, when nearly everybody else is awake and making a noise. Many of us who live in cities would like to be able to close our ears sometimes.

Mr. Bolles tells a story about the sharp hearing of a heron. The bird was on a tree dressing his plumage, and he was hidden in some bushes and could not be seen.

Mr. Bolles made all sorts of noises to start up the heron and make him fly. First he imitated animal sounds. He quacked, and barked, and mewed, and brayed, and the bird looked interested, but not at all alarmed. Then he whistled and sang, and at last talked plainly, but the bird only looked over his way, as if to see what new sort of beast was hidden there.

No noise that he could make startled the heron in the least, until a twig snapped under his foot, when the bird was off like a shot. That sound he well knew was made by his most feared enemy, man.

XXIV

HIS FEET AND LEGS

A BIRD always stands on his toes, not on his whole foot, as we do. The long slim part that we call the leg is really the foot, and the joint we see nearly up to the bird's body is the bird's heel. But in this book we will speak of it in the common way, calling the toes the foot, and the part up to the joint the leg.

People all over the world have the same kind of feet and the same number of toes; but with birds it is not so. Most of them have four toes (Fig.

8), but some have only three, and a few have no more than two.

[Ill.u.s.tration: FIG. 8.

Foot of Blackbird.]

In the use of the feet there is still more variety. There are, as Dr.

Coues divides them, three kinds of feet among birds:--

[Ill.u.s.tration: LESSER YELLOWLEGS]

First, a foot that can be used like a hand to clasp a perch, a "perching foot."

Second, one that is good to use as a foot, but not at all like a hand, called a "scratching foot."

Third, one that is like neither hand nor foot, but a paddle, called a "swimming foot."

The birds who have the first kind, the "perching foot," have usually three toes turned forward and one turned back. They can grasp a branch or a twig as tightly as if with a hand, as all our common little birds do. And the large birds of prey, such as hawks and owls (Fig. 9), hold in them live mice and squirrels and the other little animals they eat.

[Ill.u.s.tration: FIG. 9. Foot of Hawk.]

Some birds with perching feet have the toes placed another way.

Woodp.e.c.k.e.rs have two turned forward and two turned back, so that they can hold better to a tree trunk (Fig. 10).

[Ill.u.s.tration: FIG. 10. Foot of Woodp.e.c.k.e.r.]

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.

XXV

HIS WINGS AND TAIL

A BIRD'S wing does not look much like our arm and hand, yet the bones show that they are the same. The bird has a shoulder, elbow, and wrist, as we have. He even has fingers, though they are so covered up by feathers that one would never know it. He has not so many fingers as we have, and they are not movable like ours.

A bird's wing is a wonderful flying-machine, which men have been trying to imitate these many years. It is made of long stiff feathers, which fold down smoothly over one another at his side when he is resting, but can spread in an instant into a broad fan, to beat the air and carry him away.

One would not think that feathers could have so much power; but when the wing is spread, the barbs of the feathers hook together with tiny hooks, so small a microscope is needed to see them; and that, together with the edges lapping over each other, makes them almost like one solid surface.

Wings are not alike in shape. The wing of a swallow is long and narrow, while that of a hen or grouse is short and round. We can tell by the shape of a wing how a bird flies.

A long, narrow, pointed wing shows that the bird has an easy, skimming flight,--either he flies great distances, or spends hours at a time on wing (Fig. 11).

[Ill.u.s.tration: FIG. 11.

Wing of Swift.]

The short round wing (Fig. 12) shows that a bird has a strong flight for short distances. These wings are found mostly on rather heavy birds, like grouse.

[Ill.u.s.tration: FIG. 12.

Wing of Sparrow.]