The body generally is clothed with feathers, remarkable structures which are as characteristic of birds as hairs are ([p. 220]) of mammals. The great majority of the feathers are small, overlapping and plate-like, with their free ends pointing backwards; and they form a light, warm, and smooth covering which is admirably adapted to the animal’s needs. Certain large feathers, carried by the wings and tail, are used in flight. The legs are feathered to the ankle-joint, but the feet are covered only with scales. The general colour of the dovecote pigeon is a slaty blue.
The head is rounded, and terminates in front in a horny bill, which does not bear teeth. At the base of the upper beak there is, on each side, a whitish patch of swollen skin called the cere, which surrounds the opening of the nostril. The eyes are large and round; in addition to upper and lower eyelids, each is provided with a transparent third eyelid, which can be flicked rapidly across the eyeball. Birds generally have very powerful sight and depend more upon this sense than upon any other. There are no external ears, but when the feathers are separated, a little below and behind the eyes, a pair of apertures leading to the internal ears may be seen.
Habits.—The pigeon lives upon grain, which it picks up by means of its horny bill. The length and flexibility of the neck are a great help in feeding. The food is swallowed immediately and passed into a large bag called the crop, which is really a dilatation of the lower part of the gullet. Here it is macerated for some time before it passes onward to the true stomach. The hinder part of the stomach is called the gizzard; it has very thick walls and a hard horny lining. In the gizzard the food is ground up by the aid of small stones which the pigeon swallows for the purpose. The stomach is followed by a much-coiled intestine, in which the process of digestion is completed.
The pigeon differs from many birds in walking instead of hopping. When perching, it bends its legs at the ankles, an action which automatically closes the toes in such a manner that the perch is grasped behind by the first toe and in front by the second, third, and fourth. The weight of the body is sufficient to maintain a tight clasp upon the perch, so that the bird is able to sleep comfortably in this position.
Fig. 179.—A Falcon. The regions of a bird’s body.
The hen-pigeon lays two white eggs, which are sat upon by the parents for fourteen days and thereby kept at a temperature of about 40 degrees Centigrade. The young birds then break through the shell and are hatched. As the chicks are at first quite helpless and unable to feed themselves, the parents supply them with a milky fluid secreted by their crops. This is sometimes called “pigeon’s milk.” Newly hatched pigeons are covered with fine feathers called down, which are pushed off by the development of the permanent feathers beneath them. The nests of wood-pigeons ([Fig. 180]) are usually built in trees; they are somewhat rough structures, composed of twigs, and open at the top.
