Birds

(bůrdz.) [A.S.] (Zool.) A cla of animals comprising all oviparous vertebrates which are clothed with feathers, furnished with a bill, and organized for flight. They have warm blood, and a complete double circulation. They are all bipeds; the body is inclined before their feet, the thighs are directed forward, and the toes elongated, forming a broad supporting base. The head and neck are more or le prolonged, the latter very flexible, and generally containing twelve or more vertebræ. The posterior extremities present five principal modifications, affording characters which distinguish five primary orders (Fig. 84). In the first order the foot (a)has three toes before and one behind, all armed with long, strong, crooked, and more or le retractile talons, adapted to seize and lacerate a living prey; this structure is a ociated with a strong, curved, sharp edged and sharp-pointed beak, often armed with a lateral tooth; a very muscular body, and capability of rapid and long-continued flight. This order is termed Raptores or Acc i pit res. The second type of foot presents three toes before and one behind, and placed on the same level; slender, flexible, of moderate length, and provided with long, pointed, and slightly curved claws. The two external toes are united by avery short membrane. A foot so constructed (b) is especially adapted for the delicate operations of nest-building, and for grasping and perching among the slender branches of trees; hence the order so characterized has been termed In se ores, and, from including the smaller tribes of birds, Pa eres. In the third type of foot(c) the hinder toe is raised above the level of the three anterior ones; this le ens the power of perching; but the other toes are strong, straight, and terminated by robust obtuse claws, adapted for scratching up the soil, and for running along the ground; the legs are for this purpose very strong and muscular, and the order SO characterized is termed Rasores, or Gallinæ. The modification by which birds are enabled to wade and b seek their food in water along the margins of rivers, lakes, and estuaries, is gained simply by elongating the bones of the leg (tibia and metatarsus), which are covered with a naked scaly skin (d). The three anterior toes are very long and slender, as in the Parra Jacana, by which the bird can support itself upon the broad floating leaves of aquatic plants; sometimes the toes are united by intervening webs (e); the legs are Fig.84. placed behind the centre of TYPES OF BIRDS' FEET. equilibrium; the body is protected by a dense covering of feathers, and a thick down next the skin; and the whole organization is especially adapted for aquatic life. Hence the order is termed Nat a to res. [s. 94] Bird's - eye. (Bot.) See PRIMULA. Bird's - eye. (Bot.) See PRIMULA. [s. 95] IMG:p0124_0.jpg:Gravür