Billbird

Bill (bird), the horny covering of the jaws of birds, often used to include the bones enclosed in and supporting this horny sheath. These bones consist of an upper and a lower half, technically called the superior and the inferior mandible respectively. The former is made up almost entirely of the intermaxillary bones (which are greatly elongated) with the superior maxilla on each side. The latter is at first composed of twelve pieces, six on each side; but in the adult bird these unite, and form a single bone, more or less resembling the letter V laid on its side (<). The bill varies greatly in form and hardness in the different orders of birds, and even in the birds of the same orders. These peculiarities will be described in treating of the groups in which they occur. The primary function of the bill is to take food, but it is also used as a weapon of offence and defence, to carry and arrange fhe materials for the nest, to dress the feathers, to feed the young brood, as a prehensile organ, and sometimes as an organ of touch. In this latter case (as in the ducks, snipes, etc.), the texture is moderately soft, and filaments of the fifth nerve ramify through it. At the base of the bill in some birds there is a fleshy scale called the "cere," which probably also serves as a tactile organ. The nostrils are placed at the base of the bill in most birds, but they may occur in almost any part of the upper mandible; in the apteryx they are at the extremity, and in the petrels they are tubular, and situated above and not in the bill. All living birds are toothless, but in some forms the bill is notched [Birds of Prey], and in others the margins of the bill are finely serrated as in some Divers. But the earliest forms known possessed true teeth [Archaeopteryx, Odontornithes], and traces of teeth (dental papillae) have been found in the young of certain parrots.