American crow

Name and taxonomy

Christian Ludwig Brehm described the American crow in 1822. The name Corvus brachyrhynchos means short-billed crow. It joins two Greek words, one for short and one for a bill. The International Ornithologists' Union settled on American crow as the official English name. Three to five subspecies are recognised, and the count depends on the authority.

The races differ mostly in the size and shape of the bill. Birds grow larger towards the northeast and smaller in the far west and the south. The eastern crow is the largest, and the southern crow is small with a small bill. The Florida crow is mid-sized, with short wings but a long bill and long legs. The northwestern crow was treated as its own species until 2020. The American Ornithological Society then folded it into this species as a regional form.

Evolution and relatives

The American crow belongs to the Corvidae, the family of crows, ravens, jays and magpies. A study of the genus Corvus in 2012 dated its split from the Old World crows. It parted from the line of the carrion, hooded and collared crows about 5 million years ago. It fills in North America the place that the carrion crow fills in Europe. The two birds probably live much the same way in much the same country.

The common raven is the confusing relative in the field. A raven is much larger, hoarser, and carries a heavier, curved bill. In flight the raven shows a wedge-shaped tail and a bigger head. A raven soars for long stretches, while a crow rarely glides more than a few seconds. The fish crow is harder still, and the two look almost identical. A fish crow puffs out its throat feathers when it calls, and the American crow does not.

Appearance

The bird is glossy black over the whole body. The legs and toes are strong, and stiff bristles cover the nostrils. The bill is black with a slight hook at the tip. It measures 3 to 5.5 cm, and the length varies a great deal by region. The body length runs 40 to 53 cm and the wingspan 85 to 100 cm. The tail measures 13.5 to 19 cm and the weight 316 to 620 g.

Males run slightly larger than females, by about a fifth in some measures. Otherwise the sexes look the same. A young crow is nearly adult size but has blue eyes and a pink mouth. Both darken as the bird matures. Its tail feathers end in points rather than the broad flat tips of an adult. Its first-winter wing and tail feathers wear brown and ragged before the first moult.

Habitat and range

The range stretches from the Pacific to the Atlantic across Canada. It runs south through the whole United States and into northern Mexico. Birds also reach the French islands of Saint-Pierre and Miquelon. Bermuda has recorded the species since 1876. Only tundra lies outside the range. GBIF holds occurrence records from 7 countries and territories.

The bird takes open country with trees close by. Farmland and grassland give it ground to forage over. Woodlots and forest edges give it places to nest and roost. It also thrives in suburbs, city parks and along the coast. Tree planting and fire control on the Great Plains let the crow spread west over the last century. Most United States birds stay put, while Canadian birds move south for the winter.

Diet and feeding

The American crow eats almost anything it can handle. In the breeding season it takes insects, larvae, worms, fruit, grain and nuts. It hunts mice, frogs and young rabbits, and it raids the nests of smaller birds. It scavenges roadkill, rubbish and stranded fish on a shore. In autumn and winter it turns more to acorns, walnuts and other nuts. Maize and wheat are favourites wherever a field offers them.

The bird forages mostly on foot, walking the ground or a branch and picking items up. A few birds work a small area, or a flock spreads across a large one. A crow holds a nut under one foot and hammers it open with the bill. It carries a walnut or a clam into the air and drops it onto rock or road. It hides meat and nuts in many small caches rather than one store. A cache sits in a tree crevice or on the ground under leaves.

The species is one of the few birds seen to modify and use a tool for food. A 2023 study found females better at the task than males. Crows also steal, and they work together to do it. One group robbed a river otter, with a bird pecking its tail while the others took the fish. Farmers long counted the crow a pest of orchards and cornfields. The insects it removes may pay back much of the damage it does.

Behaviour and social life

Crows are cooperative breeders and live in extended families. A family can hold up to 15 birds from several seasons and stay together for years. Young from an earlier brood stay on to help feed the next one. Every member of the family joins in driving predators off the territory. Family members preen each other, which keeps the bonds strong. A third kind of group is the floater flock, of up to 50 unpaired birds.

Outside the nesting season the birds gather to sleep in huge communal roosts. Roosting builds through autumn and peaks in midwinter. Tens of thousands, and sometimes far more, assemble in tall trees in the late afternoon. The flock often shifts to a final site at nightfall. Some birds still hold their territory through the winter and commute to the roost. Crows also mob a hawk or an owl together, calling harshly as they chase it.

The species ranks among the cleverest birds. Its brain weighs as much against its body as a human brain does. Studies point to self-awareness, and young birds learn from patient parents. A crow uses the pallium of its brain where a mammal uses the neocortex. Crows remember and identify individual people by appearance. They also play, and one bird was seen sliding down a roof on a piece of bark.

Communication and senses

The familiar call is a loud, hard caw repeated three or four times. The bird throws its head up and down as it delivers the call. Males and females use the same songs, which is unusual among songbirds. A short sharp caw serves as an alarm. A longer caw defends the territory, and neighbours answer each other in patterns. A doubled caw calls the family to deal with an intruder.

Much of the repertoire is quiet and little known. Soft musical coos pass between family members, with a bow of the head. Birds kept together come to coo alike, which may explain why pet crows copy speech. Crows also produce several kinds of rattle. A young bird gargles, and the sound turns into adult calls over time. A yearling rambles through long runs of different rhythms.

The species copies other sounds as well. Wild birds have imitated other animals, including barred owls. Harsh cawing accompanies the mobbing of a predator. Pairs and families sometimes caw in chorus. Sharp eyesight probably guides the bird to food and lets it know a human face.

Reproduction and life cycle

The pair is socially monogamous and holds one territory. Breeding runs from February through June. Some birds sit on eggs by early April. Both sexes build a bulky basket of sticks, twigs and strips of bark. The nest usually sits high in a sturdy tree, and oaks are the commonest choice. Nests in bushes are unusual, and nests on the ground are very rare.

A clutch holds three to six eggs, dull blue-green or grey-green with brown blotches. The female sits for about 18 days while her mate brings her food. She begs from him at the nest like a chick. The young leave the nest about 35 days after they hatch. Both parents feed them, and older siblings help. Fledglings stay clumsy for weeks and are guarded through the summer.

A pair raises one brood a year and may try again if an early nest fails. Birds reach breeding age at two years old. Most do not leave home to breed until four or five. The average life in the wild is 7 to 8 years. The oldest banded wild bird reached 14 years and 7 months, and AnAge gives a maximum of 20. Captive crows have lived up to 30 years.

Predators and threats

Most losses happen at the nest. Snakes, raccoons, ravens and domestic cats take the eggs and the nestlings. Great horned owls, red-tailed hawks and peregrine falcons kill adults. Both North American eagles do so too. A careless bird at carrion may fall to a coyote or a bobcat, though that is rare.

West Nile virus is the heaviest blow the species has taken. The virus reached North America in 1999 and spread through mosquitoes. Crows die from it more readily than most birds. A local population can lose up to 72% of its birds in one season. The species may have fallen by as much as 45% since 1999. Because the birds die so fast, health services watch them to track the virus.

Population and conservation

BirdLife International estimated 31 million American crows in 2012. The IUCN Red List places the species in Least Concern. The wide range and large numbers keep it far from danger. iNaturalist holds 218,861 observations of the bird. Suburban growth appears to suit the species, and numbers there may still be rising.

People have killed crows in enormous numbers. Between the 1900s and the 1950s, state campaigns dynamited whole roosts. One programme in Oklahoma destroyed 3.8 million birds between 1934 and 1945. The population barely moved, and crop damage did not fall, so the work stopped. A study of bands recovered from 1917 to 1999 found deliberate killing behind 68% of deaths. Canada gives the crow no protection outside Quebec, which bars hunting in the nesting season.

Relationship with humans

Few wild birds sit as close to daily human life as this one. Crows follow rubbish, feed at landfills and scatter what they cannot eat. A large roost near houses brings noise, mess and worry about disease. Flocks in orchards and cornfields do real damage to a crop. The true cost to farming is poorly measured.

Farmers have tried many ways to move crows on. Netting protects a high-value crop but costs too much for most fields. Scaring works for a while, with guns, kites shaped like hawks and recorded distress calls. Reflective tape on a fence and a plastic owl that turns in the wind do the same job. Crows learn to avoid a bait that has made them ill. Some scientists argue that the birds help farmers by eating pests and chasing hawks off stock.

Crows cannot pass West Nile virus straight to a person. Hunting rules differ from state to state. New Jersey allows a short season, and Oklahoma permits shooting even while the birds nest. Keeping a crow is illegal under the Migratory Bird Treaty Act, though people still do it. Hand-reared birds learn to copy human speech.

In culture and myth

Western tradition links crows with death, graveyards, theft and ill fortune. The habit of feeding at carrion sits behind much of that. The loud calls and the black plumage probably add to it. Aesop put the bird in two well-known fables. In The Crow and the Pitcher a thirsty crow drops stones in to raise the water. In The Fox and the Crow a flatterer talks a crow out of its cheese.

Native American traditions read the bird very differently. Many nations treat a crow sighting as a piece of good fortune. The stories dwell on its cleverness rather than on death. Crow clans exist among the Chippewa, Hopi, Menominee, Caddo, Tlingit and Pueblo peoples. Hopi tradition holds a Crow Mother figure. A Lenni Lenape story sends the Rainbow Crow to fetch fire for the people.

Plains stories tell how the crow gained black feathers through its bond with the buffalo. In a Chippewa story, children who will not obey become crows. A Gros Ventre story leaves the crow as the one animal to survive the great flood. Some nations treat crow and raven as one figure, while others keep them apart. Neopagan writers tie the bird to gods such as Apollo and Odin.