The Beak.—The beak, bill, or neb of a bird is formed of two horny sheaths, overlying bony supports, and forming the mouth and food-get ting organ of a bird. It consists of two mandi bles. an upper and a lower, into which the fore most bones of the skull are produced, all appear ance of lips being lost. It is not furnished with proper teeth, although rudiments of them have been observed in the embryos of some parrots; and the marginal lamina; with which the bills of many water-fowl are furnished partake of the same character, being secreted by distinct pulps. The resemblance of these marginal !anti nT to teeth is particularly marked in the mer ganser (q.v.). The bills of birds differ much, according to their different habits, and particu larly according to the kind of food on which they are destined to live, and the manner in which they are to seek it. In birds of prey, the beak is strong: the upper mandible arched or hooked. and very sharp; the edges sharp, often notched, and the whole beak adapted for seizing animals, and tearing and cutting to pieces their flesh. A powerful, short, hooked beak, sharp edged and notched, indicates the greatest courage and adaptation to preying on living animals. The beak of the vulture is longer and weaker than that of the eagle or falcon. In birds which feed on insects and vegetable substances, the hooked form of the beak is less common. though well marked in parrots: those birds which catch insects on the wing, such as the night jars, swifts. etc.. are remarkable for the deep division of the beak, and their consequently wide gape, and an analogous provision to facilitate the taking of prey is to be observed in herons, kingfishers. and other fishing birds: but the ob ject is attained in their case by the elongation of the beak, whereas birds which catch insects on the wing have the beak -very short. Birds which feed chiefly on seeds have the beak short and strong, for bruising them: while the beak of insectivorous birds is comparatively slender.
Many aquatic birds have broad, comparative ly soft and sensitive bills, with lamina on the inner margin for straining the mud from which much of their food is to be extracted; other birds, as snipes, avocets. etc., seeking their food also in mud, have slender bills of remarkable sensibility. As the varieties of form roughly distinguished the larger and more obvious of the groups of birds, the bill was made the stand ard for the early classifications, giving such group-names as Deal rostres, Coni rostres, etc., no longer of scientific value. The modifications of form are very numerous. and the peculiarities of the bills of toucans. hornbills, spoonbills, crossbills, parrots, humming-birds, etc., are very interesting. and intimately connected with habits. Some of the modifications, however, are sexual and transitory, such as the knob on the beak of the pelican, and the deciduous parts of that of the puffin. At the base of the upper mandible, a portion of the beak is covered with a mem brane. called the ccrc (Lat. ccra, wax, from the waxy appearance which it presents in some fal cons. etc.), which in many birds is naked, in others is feathered,and frequently is covered with hairs or bristles. The nostrils are situated in the upper mandible, usually in the eere, but in some birds they are comparatively far forward, and in some, as puffins, they are very small and placed so near the edge of the mandible as not to be easily detected. They are more or less open,
or covered with membrane. or protected by hairs or feathers. Besides their principal use for seizing and dividing or triturating food, the bills of birds arc employed in a variety of func tions• as dressing or preening the feathers, con structing nests, etc. They are also the principal instruments used by birds in their combats.
The Fcet.—The feet of birds vary considerably, according to their mode of life. In some the claws are strong and hooked, in others short, straight. and weak; in some the toes are all sepa rate. in others more or less connected; in birds especially adapted for swimming they are gen erally webbed or united by a membrane; in other swimming birds, however, a membrane extends only along the sides of each toe. A large group of birds, including woodpeckers, parrots, etc., have two toes before, opposed by two behind, the foot being thus particularly adapted to grasping irregular surfaces and facilitating climbing. These distinctions were seized upon by the early ornithologists as a means of classification, which gave us such obsolete group-names as Scan sores, Rasores, etc., which only partly coincide with the more scientific groupings now aeeept ed. in most birds the tibia is feathered to the heel-joint ; in some, however, and particularly in waders, the lower part of it is bare: the shank and toes are generally destitute of feath ers. and are covered with scaly skin, and the arrangement of these scales has been much stud ied. "The most primitive form of the horny covering of the feet." according to Stcjneger, "seems to be its division into uniform hexago nal scales, and is called reticulate; the next. stage is when some of these scales fuse together, forming what are termed scuts, or scutella; . . . still further specialization is indicated by the tarsal scan fusing into a continuous covering. which, in its extreme development. embraces both the front and the back of the tarsus. as in some of the higher groups of passerine birds: such a tarsus is said to he 'booted.'" Feet, like beaks, have certain accessory or ehangeable parts: thin in the grouse family there is a seasonal molting of the sheaths of the claws. The most important appendage, however, is the spur or series of spurs, which arm the 'heels' of .certain gallina mous cock•• birds, and form serviceable weapons among this Mass, whose beaks are ill adapted to use as weapons, so that they strike with feet and wings in their combats. The extraordinary development of the legs and feet in ratite birds will be found described under MOA, OS•RICO, and OilM/and.—The skin of birds has no sudorifer ous nor glands, but on the rump at the base of the tail (on the 'pope's nose') is a bilobed gland containing oily matter, which is present in all birds except the Ratite, bustards. and a few others. This secretion seems useful only for cleaning the plumage, and the bird squeezes a little out upon its beak before preen ing its feathers. In the oil-bird the secretion is excessive, and that of the hoopoe has a very disa greeable odor.