Crow (bird) - biology.

Crow (bird) - biology. Crow (bird), common name for about 27 large passerine birds of the genus which also includes the ravens and jackdaws. Their family also includes the jays, magpies, choughs, and nutcrackers. Crows are found on every continent except South America and Antarctica. They are among the most intelligent and adaptable of birds, and several species have been able to thrive near humans, although others, especially on islands, are endangered and their habits little known. Northern-hemisphere crows are sometimes migratory, but often they are resident the year round. Although territorial in the breeding season, crows are gregarious at other times, and wintering flocks may number in the thousands. Even in the breeding season, crows gather together to mob owls and other predators. Crows in turn may be mobbed by other birds, because their omnivorous diet includes eggs and nestlings as well as other small animals, vegetable matter, carrion, and garbage. In some agricultural areas, crows are considered great pests, which accounts for the invention of the scarecrow. Crow nests are large platforms of sticks, usually in tall trees. The three to eight eggs are deeply colored and are incubated by the female. The young are cared for by both parents. The voices of crows are loud and usually harsh, but are characteristic for each species. All of the North American crows are black, with more or less of a glossy sheen, but several species from elsewhere are conspicuously marked with white or gray. The best known species is the ubiquitous American crow, which has become increasingly adapted to urban areas in the late 20th century. The American crow is up to 50 cm (up to 20 in) long and has an average lifespan of approximately 15 years in the wild. A similar species, differing in voice, is the northwestern crow, confined to the Pacific coast from Alaska to Oregon. A smaller, glossier species, the fish crow, lives along the Atlantic and Gulf coasts from New England to Texas and inland along major river systems. The tiny Mexican crow, also known as the Tamaolipas crow, is regularly seen in southeasternmost Texas. Scientific classification: Crows belong to the family Corvidae of the order Passeriformes. The American crow is classified as Corvus brachyrhynchos, the northwestern crow as Corvus caurinus, the fish crow as Corvus ossifragus, and the Mexican crow as Corvus imparatus. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.