/ bɝːd /
ETYM Old Eng. brid, bred, bird, young bird, bird, AS. bridd young bird.
1. The flesh of a bird or fowl (wild or domestic) used as food; SYN. fowl.
2. Warm-blooded egg-laying vertebrates characterized by feathers and forelimbs modified as wings.
Backboned animal of the class Aves, the biggest group of land vertebrates, characterized by warm blood, feathers, wings, breathing through lungs, and egg-laying by the female. There are nearly 8,500 species of birds.
physical structure and ability.
Birds are bipedal, with the front limb modified to form a wing and retaining only three digits. The heart has four chambers, and the body is maintained at a high temperature (about 41şC/106şF). Most birds fly, but some groups (such as ostriches) are flightless, and others include flightless members. Many communicate by sounds (nearly half of all known species are songbirds) or by visual displays, in connection with which many species are brightly colored, usually the males. Birds have highly developed patterns of instinctive behavior.
senses and feeding.
Hearing and eyesight are well developed, but the sense of smell is usually poor. No existing species of bird possesses teeth. The tongue aids in feeding, and there is frequently a dilation of the esophagus, called the crop, where food is stored and softened. The stomach is small with little storage capacity and usually consists of the proventriculus, which secretes digestive juices, and the gizzard, which is tough and muscular and grinds the food, sometimes with the aid of grit and stones retained within it.
Typically eggs are brooded in a nest and, on hatching, the young receive a period of parental care.
The study of birds is called ornithology.
Within individual species, males may defend an area or territory against competing males. The size of territory varies between species. The gannet, a seabird which nests in dense colonies on cliffs and rocky islets, may defend an area encompassing only the extent to which the sitting female can jab with her bill, whereas the robin defends a territory of just over an acre.
Once a songbird has selected its territory, it will sing to fulfill the dual purpose of advertising its presence to rival territory holders and attracting a female. The song must signify to the female that the singer is a territory-holding male of the correct species in breeding condition, therefore it is important as a species-isolating mechanism. Closely related species that overlap in some habitats often have conspicuously different songs, for example the chiffchaff and willow warbler. A song must be sufficiently stereotyped to be recognizable to other members of the species, but there is still room for much variation within these confines. Thus individual chaffinches may possess several different songs within their repertoire, all recognizable chaffinch songs, but differing perhaps in the number of notes in the song or in the type and arrangement of these notes. In species that do not sing, visual display may perform the same functions as song.
Different bird species occupying the same area usually have different food requirements, different nesting habits, and specific song and courtship behavior, which not only prevents interbreeding but also reduces competition between species.
The oldest bird known, archaeopteryx, lived in Jurassic times, about 140 million years ago. Its reptilian features include teeth, a well-marked tail, with many separate vertebrae, and claws on the wing digits (claws also occur in the embryo ostrich), but it has feathers, hence is classed as a bird.
/ faʊl /
ETYM Old Eng. foul, fowel, foghel, fuhel, fugel, AS. fugol.
Chicken or chickenlike bird. Sometimes the term is also used for ducks and geese. The red jungle fowl Gallus gallus is the ancestor of all domestic chickens. It is a forest bird of Asia, without the size or egg-laying ability of many domestic strains. Guinea fowl are of African origin.