Американская ворона (Corvus brachyrhynchos)

Species of bird

The American crow (Corvus brachyrhynchos) is a large passerine bird species of the family Corvidae. It is a common bird found throughout much of North America. American crows are the New World counterpart to the carrion crow and the hooded crow of Eurasia; they all occupy the same ecological niche. Although the American crow and the hooded crow are very similar in size, structure and behavior, their calls and visual appearance are different. From beak to tail, an American crow measures , almost half of which is tail. Its wingspan is Mass varies from about , with males tending to be larger than females. Plumage is all black, with iridescent feathers. It looks much like other all black corvids. They are very intelligent, and adaptable to human environments. The most usual call is They can be distinguished from the common raven (C. corax) because American crows are smaller and the beak is slightly less pronounced; from the fish crow (C. ossifragus) because American crows do not hunch and fluff their throat feathers when they call; and from the carrion crow (C. corone) by size, as the carrion crow is larger and of a stockier build. American crows are common, widespread, and susceptible to the West Nile virus, making them useful as a bioindicator to track the virus's spread. Direct transmission of the virus from crows to humans is impossible. They are considered an agricultural pest, and are subject to hunting and management.

The American crow was described by German ornithologist Christian Ludwig Brehm in 1822. "American crow" has been designated the official name by the International Ornithologists' Union (IOC).

The number of subspecies varies by authority, ranging between three and five. The unclear taxonomy of the northwestern crow, previously its own species, has complicated subspecies determinations. Subspecies differ in bill proportion and form a rough NE–SW clinal in size across North America. Birds are smallest in the far west and on the southern coast. C. b. brachyrhynchos (Brehm, 1822) – eastern crow: northeastern United States, eastern Canada and surroundings. The nominate subspecies, and largest. C. b. hesperis (Ridgway, 1887) – western crow: western North America except the Arctic north, the Pacific Northwest and the extreme south. Smaller overall with a proportionally more slender bill and low pitched voice. C. b. caurinus (Baird, 1858) – northwestern crow: of the Pacific temperate rain forests was formerly considered a distinct species as C. caurinus, averaging smaller in size than other American crows with a distinctly hoarser call. The American Ornithological Society lumped the northwestern crow with the American crow in 2020. It is now considered a geographic variation within C. b. hesperis. C. b. pascuus (Coues, 1899) – Florida crow: Florida. Mid sized, short winged, but decidedly long bill and legs.

The American crow is a large, distinctive bird with iridescent black feathers all over. Its legs, feet and bill are also black. They measure in length, of which the tail makes up about 40%. The wing chord is , with the wingspan ranging from The bill length can be from , varying strongly according to location. The tarsus is and the tail is
The most usual call is a loud, short, and rapid 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, such as barred owls. 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 fish crow's 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 and their larger looking heads. They also fluff their throat feathers when calling – like fish crows, only more so. Ravens also soar for extended periods, unlike crows, which rarely fly more than a few seconds without flapping their wings. Crows have been noted to be intelligent. They have the same brain weight to body ratio as humans. This has led to some studies that have identified that crows are self aware and that young crows take time to learn from tolerant parents. While a human has a neocortex, the crow has a different area in their brain that is equally complex. The average lifespan of the American crow in the wild is 7–8 years. Captive birds are known to have lived up to 30 years. as well as range expansions of many other species of birds. Virtually all types of country from wilderness, farmland, parks, open woodland to towns and major cities are inhabited; it is absent only from tundra habitat, where it is replaced by the common raven. This crow is a permanent resident in most of the US, but most Canadian birds migrate some distances southward in winter. Outside of the nesting season these birds often gather in large (thousands or even millions) communal roosts at night. The American crow was recorded in Bermuda from 1876 onwards.

Studying the behavior of American crows is laborious due to the difficulty in catching them to band them, let alone catching them again. Thus much of their behavior, including daily routine, migration, molting, survivorship, age of first breeding, nestling development, and the nature of nesting helpers, remains poorly studied. It will feed on invertebrates of all types, carrion, scraps of human food, fruits, nuts such as walnuts and almonds, seeds, eggs and nestlings, stranded fish on the shore and various grains. American crows are active hunters and will prey on mice, young rabbits, Offspring from a previous nesting season will usually remain with the family to assist in rearing new nestlings. American crows do not reach breeding age for at least two years.

American crows succumb easily to West Nile virus infection. This was originally a mosquito borne African virus causing encephalitis in humans and livestock since about 1000 AD, and was accidentally introduced to North America in 1999, apparently by an infected air traveller who got bitten by a mosquito after arrival. It is estimated that the American crow population has dropped by up to 45% since 1999. Despite this decline, the crow is considered a species of least concern. The disease runs most rampant in the subtropical conditions which encourage reproduction of its mosquito vectors among which Culex tarsalis is most significant. Mortality rates appear to be higher than those in other birds, causing local population losses of up to 72% in a single season.

Crows are used as a motif in some human cultures, often associated with death, thieves, graveyards, bad luck, and other negative connotations. Conversely, they are seen by some neo pagan and indigenous cultures as signs of good luck, or even signs of certain gods, such as Apollo, Odin, and others.

The intelligence and adaptability of the American crow has insulated it from threats, and it is instead considered an agricultural pest.