Crows will group together to vocally harass and chase predators. This behavior is called mobbing.
Known Predators:
American Crows are highly vocal birds. Unlike most other songbirds, males and females have the same songs. They have a complex system of loud, harsh caws that are often uttered in repetitive rhythmic series. Shorter and sharper caws called "kos" are probably alarm or alert calls. Slightly longer caws are probably used in territorial defense, and patterns of repetition may be matched in what may be considered "countersinging," or exchanges between territorial neighbors. "Double caws," short caws repeated in stereotyped doublets, may serve as a call-to-arms vocalization, alerting family members to territorial intruders. Sometimes pairs or family members coordinate their cawing in a duet or chorus. Harsher cawing is used while mobbing potential predators.
People are less familiar with the large variety of softer calls crows can make. Melodic, highly variable coos accompanied by bowing postures are used among family members, possibly as greetings or other bonding signals. Coos of cage-mates become similar over time; this vocalization may therefore be the basis of the mimicry ability shown by pet crows. Crows also give several kinds of rattles.
Young crows make gargling sounds that eventually turn into adult vocalizations. Yearling crows also "ramble" or run through long sequences of different patterns and rhythms of cawing.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
American crows are thriving, particularly in association with suburban areas. Their numbers may be increasing.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Large foraging flocks of American crows may impact agriculture, particularly orchards and cornfields. In the United States there once was a bounty on them. People often consider large roosts to be nuisances when they occur in areas with high human activity; there is concern about noise, mess, and disease from feces. American crows can scatter garbage. As nest predators they may negatively impact population of game birds such as ducks.
Negative Impacts: crop pest
Although American crows can be harmful to crops, their impact is shown to be less than what it was previously thought to be. Damage to crops is offset by the amount of damage prevented because the crows eat insect pests. Though it is illegal under the Migratory Bird Act, many people have kept young crows as pets and they are known to mimic human speech. American crows are also considered small game, and hunting seasons exist in many states. Typically they are hunted for sport at times when more valuable game birds cannot be hunted.
Positive Impacts: controls pest population
American crows do not have significant, unique roles in particular ecosystems. They probably serve as seed dispersers as they eat fruit and cache nuts. They scavenge on carcasses which speeds their decomposition.
Ecosystem Impact: disperses seeds; biodegradation
American crows are omnivores and will eat almost anything. During the breeding season, American crows consume insects and their larvae, worms, fruits, grains, and nuts. They actively hunt and prey on small animals such as frogs, mice, and young rabbits, though they more likely to scavenge carrion such as roadkill. They also are significant nest predators, preying on the eggs and nestlings of smaller songbirds. In the fall and winter they eat more nuts, such as walnuts and acorns. On rare occasions, American crows will eat from bird feeders put out by humans. Crows often take advantage of human garbage.
American crows store food items such as meat and nuts in short-term caches. Caches are hiding places that are scattered around, rather than in one place. They may be in tree crevices or on the ground, where they are often covered with leaves or other material.
Crows forage primarily by walking on the ground and picking up the item, or by walking along tree branches. Foraging is usually done by a few individuals in a small area, but can also occur in groups over a larger area.
Crows will hold a nut under one foot and strike it with the bill to open it. To open a particularly heavy-shelled food item such as a walnut or clam, a crow will fly high with it and drop it on a hard surface.
Animal Foods: birds; mammals; amphibians; reptiles; eggs; carrion ; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms
Plant Foods: seeds, grains, and nuts; fruit
Primary Diet: omnivore
American crows are native to the Nearctic region all over North America. They can be found in the lower part of Canada and through the continental United States.
Biogeographic Regions: nearctic (Native )
American crows prefer open areas with nearby trees. Agricultural and grassland areas are ideal habitat for crows to forage for their food. American crows will also use nearby woodlots and forest edges for breeding and roosting. American crows thrive in suburban neighborhoods and urban parks, as well as in coastal habitats.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest ; scrub forest
Aquatic Biomes: coastal
Other Habitat Features: urban ; suburban ; agricultural ; riparian ; estuarine
The oldest recorded age of a wild American crow is 14 years and 7 months.
Range lifespan
Status: wild: 14 (high) years.
Average lifespan
Status: wild: 175 months.
Adult American crows are completely black birds weighing on average 450 g. The feathers have a glossy and slightly iridescent look. Crows have strong legs and toes. The bill is also black with a slight hook on the end. Stiff bristles cover their nostrils. About 20% of male birds are slightly larger than the females.
Young crows are about the same size as adults, but have blue eyes and pink inside the mouth. Both the eyes and mouth darken as the bird becomes an adult. In young birds, the ends of tail feathers are symmetrical and are more pointed than the wide, flat-ended feathers of adults. The wing and tail feathers of the young can become quite brown and ragged through the first winter and spring and only become darker and more glossy like adult feathers after the first molt.
American crows are often confused with common ravens. American crows can be distinguished from common ravens (Corvus corax) most easily by size (ravens are much larger), by voice (ravens are hoarser), by the bill (ravens have heavier, "roman-nosed" bills), and by the shape of the wings and tails, which come to a point in ravens but not crows.
Average mass: 450 g.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; male larger
Average mass: 384.8 g.
Breeding in American crows may begin as early as February and last through June. Nests are usually built by both males and females high in a sturdy conifer or hardwood tree. Females lay 4 to 5 light green colored eggs with brown markings. The female incubates her eggs, which means that she sits on them to keep the eggs warm until they hatch. Eggs hatch after 18 days. While she is sitting on the nest, the female will beg for food like a baby bird, and her mate will bring it to her. The young fledge (leave the nest) when they are approximately 35 days old. Most American crows reach sexual maturity and begin to breed when they are two years old.
Breeding interval: American crows rear only a single brood each year; if a nest fails early in the breeding season the pair may try to lay a second clutch of eggs.
Breeding season: Breeding occurs from February through June.
Range eggs per season: 4 to 5.
Average eggs per season: 4.
Average time to hatching: 18.0 days.
Average fledging age: 35.0 days.
Average age at sexual or reproductive maturity (female): 2.0 years.
Average age at sexual or reproductive maturity (male): 2.0 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Average time to hatching: 18 days.
Average eggs per season: 5.
Young crows are helpless at birth and require parental care. They are fed by both parents as well as by helpers who are their older siblings. After they leave their nests, young are still clumsy for several weeks and must be fed and protected by family members during the summer. Parents have been observed to feed babies even after they can find food on their own.
Parental Investment: altricial ; pre-fertilization (Protecting: Male, Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
Only slightly larger (17-21 inches) than the similar-looking Fish Crow (Corvus ossifragus), the American Crow is most easily separated from its relative by its call, which is deeper and less nasal than that of the Fish Crow. Other field marks include a glossy purple-black body, thick bill, and slightly rounded tail. The American Crow occurs widely across the United States and southern Canada, absent only from the desert southwest, south Texas and northwestern Washington (where it is replaced by the Northwestern Crow, Corvus caurinus). Many American Crows breeding in Canada move south into the U.S. during the winter. However, more southerly populations are mostly non-migratory. American Crows tend to avoid wide expanses of open country such as desert, grassland, and tundra. Otherwise, American Crows are extremely adaptable birds, and are found in many habitats across North America, including forest, orchards, fields, suburbs, and even inner cities. Likewise, this species eats a variety of plant and animal foods, including fruits, seeds, small mammals, carrion, and garbage. Like most members of the crow family, the American Crow is extremely sociable. American Crows gather together in family groups to feed, roost, and defend territory. They will even mob larger predatory birds intruding on their territory, swooping down and calling loudly until the predator leaves the area. This species is primarily active during the day.
Only slightly larger (17-21 inches) than the similar-looking Fish Crow (Corvus ossifragus), the American Crow is most easily separated from its relative by its call, which is deeper and less nasal than that of the Fish Crow. Other field marks include a glossy purple-black body, thick bill, and slightly rounded tail. The American Crow occurs widely across the United States and southern Canada, absent only from the desert southwest, south Texas and northwestern Washington (where it is replaced by the Northwestern Crow,Corvus caurinus). Many American Crows breeding in Canada move south into the U.S. during the winter. However, more southerly populations are mostly non-migratory. American Crows tend to avoid wide expanses of open country such as desert, grassland, and tundra. Otherwise, American Crows are extremely adaptable birds, and are found in many habitats across North America, including forest, orchards, fields, suburbs, and even inner cities. Likewise, this species eats a variety of plant and animal foods, including fruits, seeds, small mammals, carrion, and garbage. Like most members of the crow family, the American Crow is extremely sociable. American Crows gather together in family groups to feed, roost, and defend territory. They will even mob larger predatory birds intruding on their territory, swooping down and calling loudly until the predator leaves the area. This species is primarily active during the day.
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 40–50 cm (16–20 in), almost half of which is tail. Mass varies from about 300 to 600 g (11 to 21 oz), 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 CaaW!-CaaW!-CaaW!. 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.[2] Its scientific name means literally 'short-billed crow', from Ancient Greek βραχυ- brachy- ('short-') and ρυνχος rhynchos ('billed').[3]
A 2012 genetic analysis of the genus Corvus by Knud A Jønsson and colleagues using nuclear and mitochondrial DNA calculated that the American crow diverged from a lineage that gave rise to the collared, carrion and hooded crows around 5 million years ago.[4]
"American crow" has been designated the official name by the International Ornithologists' Union (IOC).[5]
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.[6][2]
The American crow is a large, distinctive bird with iridescent black feathers all over. Its legs, feet and bill are also black. They measure 40–53 cm (16–21 in) in length, of which the tail makes up about 40%. The wing chord is 24.5 to 33 cm (9.6 to 13.0 in), with the wingspan ranging from 85 to 100 cm (33 to 39 in). The bill length can be from 3 to 5.5 cm (1.2 to 2.2 in), varying strongly according to location. The tarsus is 5.5 to 6.5 cm (2.2 to 2.6 in) and the tail is 13.5 to 19 cm (5.3 to 7.5 in).[6] The body mass can vary from 316 to 620 g (11.1 to 21.9 oz). Males tend to be larger than females.[13][14]
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, such as barred owls.[15]
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.[16]
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.[17][18]
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.[19][20]
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.[21]
The range of the American crow now 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.[1] 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[22] as well as range expansions of many other species of birds.[23][24][25] 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[26]) communal roosts at night.
The American crow was recorded in Bermuda from 1876 onwards.[27]
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, nature of nesting helpers, and more remains poorly studied.[2]
The American crow is omnivorous. It will feed on invertebrates of all types, carrion, scraps of human food, fruits,[28] 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,[29] frogs, and other small animals. In the winter and autumn, the diet of American crows is more dependent on nuts and acorns. Occasionally, they will visit bird feeders.[30] The American crow is one of only a few species of bird that has been observed modifying and using tools to obtain food.[31]
Like most crows, they will scavenge at landfills, scattering garbage in the process. Where available, corn, wheat and other crops are a favorite food. These habits have historically caused the American crow to be considered a nuisance. However, it is suspected that the harm to crops is offset by the service the American crow provides by eating insect pests.[30]
American crows are socially monogamous cooperative breeding birds. Mated pairs form large families of up to 15 individuals from several breeding seasons that remain together for many years.[32] 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.[33] Most do not leave the nest to breed for four to five years.[32]
The nesting season starts early, with some birds incubating eggs by early April.[34] American crows build bulky stick nests, nearly always in trees but sometimes also in large bushes and, very 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 usually fledged by about 36 days after hatching. 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 eagles. They may be attacked by predators such as coyotes or bobcats at carrion when incautious, although this is even rarer.[30][35]
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.[36] Despite this decline, the crow is considered a species of least concern.[37] 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.[33][38] Because of this, American crows are a sentinel species indicating the presence of West Nile virus in an area. Crows cannot transmit the virus to humans directly.[21]
American crows, like other corvids, are highly cunning and inquisitive. They are able to steal food from other species, often in creative ways. One example shows a group of crows stealing a fish from a Northern river otter: one bird pecked the otter's tail to distract it while other birds swooped in and stole the fish.[2] They are able to use and modify tools.[39]
Crows are used as a common motif in human culture, often associated with death, thieves, graveyards, bad luck, and other negative connotations.[40]
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.[41]
The intelligence and adaptability of the American crow has insulated it from threats, and it is instead considered an agricultural pest.[2] In 2012, BirdLife International estimated the American crow population to be around 31 million. The large population and vast range result in the least concern status for the American crow, meaning that the species is not threatened with extinction.[1]
Crows have been killed in large numbers by humans, both for recreation and as part of organized campaigns of extermination.[42] In Canada, American crows have no protections, aside from Quebec which bans their hunting during the nesting season.[2] Laws on their hunting vary throughout the United States. New Jersey allows for a limited hunting season, unless if they are agricultural pests in which case they may be killed. Oklahoma allows hunting even during the nesting season. In the first half of the 20th century, state sponsored campaigns dynamited roosting areas, taking large numbers of crows. A campaign in Oklahoma from 1934 to 1945 dynamited 3.8 million birds. The effect on populations was negligible and damage to agricultural crops did not decrease, and thus the campaign was halted as ineffective. In a study taking data from 1917 to 1999, intentional killings were the overwhelming cause of death for crows, accounting for 68% of all recovered bird bands.[2]
Non-deadly methods of managing crows are varied but usually limited in their effectiveness. High value crops may be netted, but this is cost prohibitive for most other crops. Frightening may be used to disperse crows, including loud noises from guns, fake hawks flown from balloons, fake owls that move with the wind, strips of reflective tape on fences, or recordings of crow distress calls. Poisoned baits are of limited effectiveness, as only the most toxic baits work, and those are generally unacceptable for use. 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.[2] There is some suggestion that they may be a benefit to farmers, by eating insect pests and chasing off livestock predators like hawks.[40]
Pair of crows chasing away a red-tailed hawk from their nest 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 40–50 cm (16–20 in), almost half of which is tail. Mass varies from about 300 to 600 g (11 to 21 oz), 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 CaaW!-CaaW!-CaaW!. 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.
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