Saturday, April 9, 2011

American Crow

American Crow - Spec. Name: Corvus brachyrhynchos

This is a large passerine bird species of the family Corvidae. It is a common bird found throughout much of North America. In the interior of the continent south of the Arctic, it is simply called "the crow", as no other such birds occur there on any regular basis.
American Crow
It is one of several species of corvid that are entirely black, though it can be distinguished from the other two such birds in its range—from the Common Raven (C. corax) by size and behavior and from the Fish Crow (C. ossifragus) by call (but seebelow). It is also distinguished from the Raven by its smaller, more curved bill than the parallell bill of the raven, and its squared tail.
American Crows are common, widespread and adaptable, but they are highly susceptible to the West Nile Virus. They are monitored as a bioindicator. Direct transmission of the virus from American Crows to humans is not recorded to date, and in any case not considered likely.

The American Crow is a distinctive bird with iridescent black feathers all over. Its legs, feet and bill are also black. They are 40–50 cm (16–20 in) in length, of which the tail makes up about 40%. Each wing is around 27–34 cm (11–14 in) long. The bill length is on average 5 cm (2 in), varying strongly according to location.[4] Males tend to be larger than females.
The most usual call is a loud, short, and rapid caaw-caaw-caaw. Usually, the birds thrust their heads up and down as they utter this call. American Crows can also produce a wide variety of sounds and sometimes mimic noises made by other animals, including other birds.
Visual differentiation from the Fish Crow (C. ossifragus) is extremely difficult and often inaccurate. Nonetheless, differences apart from size do exist. Fish Crows tend to have more slender bills and feet. There may also be a small sharp hook at the end of the upper bill. Fish Crows also appear as if they have shorter legs when walking. More dramatically, when calling, Fish Crows tend to hunch and fluff their throat feathers.
If seen flying at a distance from where size estimates are unreliable, the distinctly larger Common Ravens (C. corax) can be distinguished by their almost lozenge-shaped tail, their larger-looking heads and of course their strongly solitary habits. They also fluff their throat feathers when calling like Fish Crows, only more so.
Most wild American Crows live for about 7–8 years. Captive birds are known to have lived up to 30 years.

Distribution and habitat
The range of the American Crow extends from the Pacific Ocean to the Atlantic Ocean in Canada, on the French islands of Saint-Pierre and Miquelon, south through the United States, and into northern Mexico. Virtually all types of country from wilderness, farmland, parks, open woodland to towns and major cities are inhabited; it is absent only from Pacific temperate rain forests and tundra habitat where it is replaced by the raven. This crow is a permanent resident in most of the USA, but most Canadian birds migrate some distances southward in winter. Outside of the nesting season these birds often gather in large communal roosts at night.
The American Crow was recorded in Bermuda from 1876 onwards.

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