Crows are large passerine birds that comprise the entire genus Corvus. Crows range in size from the relatively small pigeon-sized jackdaws from Europe and Asia to the Common Raven. There are about 40 members of this genus occuring on all temperate continents excluding South America.
American CrowBut for our purposes we will be talking exclusively about the American Crow (Corvus brachyrhynchos). The American Crow is a large bird commonly found throughout North America. They are entirely black in color, it is an easily recognized bird. There are some very rare occurances of crows with some white feathers.
American Crows have a lifespan of 7 to 8 years. Captive birds are known to have lived up to 30 years.
The most usual call is a loud, short, and rapid "caah-caah-caah". 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.
The American Crow is omnivorous meaning it eats both animals and plant material. It will feed on insects, carrion, scraps of human food, seeds, eggs and nestlings, stranded fish on the shore and various grains. American Crows are active hunters and will prey on mice, frogs, and other small animals. In winter and autumn, the diet of American Crows is more dependent on nuts and acorns and other mast both hard and soft.
Crows are monogamous cooperative breeding birds. Mated pairs form large families from several breeding seasons that remain together for many years. Offspring from a previous nesting season will usually remain with the family to assist in rearing new nestlings. Crows do not reach breeding age for at least two years.
Crows build bulky stick nests, nearly always in trees but sometimes also in large bushes and only rarely on the ground. They will nest in a wide variety of trees, including large conifers, although oaks are most often used. Three to six eggs are laid and incubated for 18 days. The young are fledged usually by about 35 days.
Due to crop damage farmers often attempt to drive away or kill these birds. Despite their efforts crows remain widespread and very common. The number of crows is estimated by Birdlife International to be around 31,000,000.
American Crows are very succeptible to the effects of the West Nile virus. Mortality rates among infected crows appear to be higher than those in other birds, causing population losses of up to 65% in some areas in a single season. Because of this, American Crows are a indicator species. But luckily crows cannot transmit the virus to humans directly.
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