American crow

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 (IOU). Subspecies 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. In 2020, the American Ornithological Society reclassified the Northwestern Crow as conspecific with the American Crow. 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. ==Description==

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, similarly to fish crows. 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 uses a different area in its brain, the pallium, to perform similar tasks. They can remember and identify people based on their appearance. 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. Distribution and habitat The American crow has a large range, extending 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. The increase in trees throughout the Great Plains during the past century due to fire suppression and tree planting facilitated range expansions of the American crow as well as range expansions of other species of birds such as the barred owl. The American crow inhabits virtually all types of country – from wilderness, farmland, parks, and open woodland to towns and major cities – and is absent only from tundra habitat. The American crow is a permanent resident in most of the US, but most Canadian birds migrate some distance southward in winter. Outside the nesting season, these birds often gather in large communal roosts of thousands or even millions of crows at night. ==Behavior and ecology==

) from their nest Studying the behavior of American crows is laborious due to the difficulty in catching them, resulting in much of their behavior, including daily routine, migration, molting, survivorship, age of first breeding, nestling development, and the nature of nesting helpers, being poorly studied. Diet The American crow is omnivorous. 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. Predation primarily occurs at the nest site, and eggs and nestlings are frequently eaten by snakes, raccoons, ravens, and domestic cats. Adults are less frequently predated but face potential attack from great horned owls, red-tailed hawks, peregrine falcons, and both North American eagles. American crows have been shown to be more wary of disturbances in urban environments. The American crow experiences inbreeding depression, yet research indicates they maintain a preference for such behavior. File:The Childrens Museum of Indianapolis - American crow egg.jpg|Egg, in the collection of the Children's Museum of Indianapolis File:Corvus caurinus - June 2007.jpg|alt=Bird on a human's hand|A fledgling, of the Northwestern subtype File:American Crow imported from iNaturalist photo 250510645 on 5 December 2024.jpg|Leucistic crow feeding its offspring West Nile virus 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. It was accidentally introduced to North America in 1999, apparently by an air traveller who was infected by a mosquito bite 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 that 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. however, unlike the Hawaiian and New Caledonian crow, this behavior is not inherent. Female crows have been observed to be better at using tools, according to a 2023 study. ==Status and management==

The intelligence and adaptability of the American crow have insulated it from threats, and it is instead considered an agricultural pest. Crows quickly learn to avoid the less toxic baits, as the baits make crows sick. The actual effect of crows on agriculture has been poorly studied. == Role in human cultures ==

Crows are used as a motif in some human cultures, often associated with death, thieves, graveyards, bad luck, and other negative connotations. However, in other cultures, like Native American folklore, crows are considered good luck, noted for their intelligence. Similarly, they are also 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. Crows are also featured in Aesop's Fables, in stories such as "The Crow and the Pitcher", and "The Fox and the Crow". ==References==