Overview

Brief Summary

Corvus brachyrhynchos

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. Fish Crow (Corvus ossifragus)The Fish Crow (Corvus ossifragus) is year-round resident locally from New York and Massachusetts south along the Atlantic-Gulf Coast to southern Florida and west to southern Texas, as well as inland along major river systems. It is very common in parts of its range. Fish Crows are found around tidewater marshes, low valleys along eastern river systems, and in Baldcypress (Taxodium) swamps; in recent decades, the interior range has expanded and the northern boundary of the range has extended northward. Although in most parts of its range it is a permanent resident, in winter Fish Crows withdraw from some parts of their inland range. In the winter, Fish Crows are often seen in mixed flocks with American Crows, when they may also be found on farmland, in towns, and around garbage dumps. The Fish Crow is one of only about a dozen bird species that are endemic to the United States (i. e. , found nowhere else in the world). The Fish Crow closely resembles the American Crow (Corvus brachyrhynchos), but is smaller overall and has a smaller bill, smaller feet, and shorter legs, as well as more pointed wings and a faster wingbeat. However, it is best distinguished by its quite different common call, a nasal two-note call with the second note lower in pitch (however, juvenile and sometimes adult American Crows produce similar calls). Fish Crows may feed on an extraordinary range of foods, including carrion, crustaceans, insects, berries, seeds, nuts, bird eggs, turtle eggs, and human garbage. They generally forage in flocks, mainly by walking, especially along the shore or in very shallow water. They may drop mollusks from the air to break open their shells. In colonies of herons and other waterbirds, if the nesting adults are frightened off their nests, Fish Crows may feast on their eggs. Fish Crows often nest in loose colonies of a few pairs. Courtship may involve the male and female flying close together in a gliding display flight. The nest is placed in an upright fork of a tree or shrub. The nest may be placed very low at coastal sites or quite high in deciduous trees in inland swamps (1 to 21 m above the ground or even higher) The nest (which is probably built by both sexes) is a bulky platform of sticks and strips of bark lined with softer materials such as grass,rootlets, hair, feathers, paper, pine needles, and even manure. The female lays 4 to 5 dull blue-green to gray-green eggs blotched with brown and gray. Incubation is by the female (possibly assisted by the male) for 16 to 18 days. Nestlings are probably fed by both parents. The age at which young leave the nest is uncertain, but is probably around 3 to 4 weeks. (© Leo Shapiro. Supplier: Leo Shapiro) CC BY

Threat Status: Least concern

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Distribution

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 )

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: north-central British Columbia to northern Saskatchewan and Newfoundland, south to northern Baja California, Texas, Gulf Coast, and southern Florida. NON-BREEDING: southern Canada south throughout breeding range. INTRODUCED: established on Bermuda (AOU 1983).

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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Geographic Range

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 )

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Physical Description

Morphology

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.

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Physical Description

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.

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Size

Length: 45 cm

Weight: 458 grams

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Ecology

Habitat

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

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Habitat and Ecology

Systems
  • Terrestrial
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Comments: Open and partly open country: agricultural lands, suburban areas, orchards, tidal flats, primarily in humid situations, restricted mostly to riparian forest and adjacent areas in arid regions. Generally avoids dense coniferous forest and desert. BREEDING: Nests in open forest and woodland, and in other wooded situations; in trees, shrubs, on utility poles, generally in crotch or near tree trunk on supporting limb, averge of about 8 m above ground.

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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

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Breeding populations north of southern Canada move south for winter.

In Washington, centers of activity of juvenile American crows were 0.2-22.2 km away from the natal territory during their first 3-12 months (Withey and Marzluff 2005).

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Trophic Strategy

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

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Comments: Opportunistic. Eats various small vertebrates, invertebrates, carrion, grain, fruits. Cooperative foraging and food caching reported in Kilham (1989).

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Food Habits

American crows are omnivores and will eat almost anything. During the breeding season, American crows consume Insecta and their larvae, Oligochaeta, fruits, grains, and nuts. They actively hunt and prey on small animals such as Anura, Sigmodontinae, and young Sylvilagus floridanus, though they more likely to scavenge carrion such as roadkill. They also are significant nest predators, preying on the eggs and nestlings of smaller Passeriformes. 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

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Associations

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

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Crows will group together to vocally harass and chase predators. This behavior is called mobbing.

Known Predators:

  • red-tailed hawks
  • great horned owls
  • raccoons
  • humans
  • snakes
  • domestic cats

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Ecosystem Roles

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

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Predation

Crows will group together to vocally harass and chase predators. This behavior is called mobbing.

Known Predators:

  • Buteo jamaicensis
  • Bubo virginianus
  • Procyon lotor
  • humans
  • Squamata
  • Felis silvestris

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Known prey organisms

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General Ecology

In southwestern Manitoba, spring-summer home range averaged 2.6 sq km; foraging flights from nest averaged 382 m, with infrequent flights longer than 700 m (Sullivan and Dinsmore 1992).

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Life History and Behavior

Behavior

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

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Communication and Perception

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

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Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 20 years
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Lifespan/Longevity

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.

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Reproduction

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)

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Clutch size 3-7 (usually 4-6). Incubation about 18 days, (?) by both sexes. Young tended by both parents, first fly at 4-5 weeks, disperse at various ages after about 2 months postfledging or stay in natal area. One or two broods annually. Auxilaries (typically young) may help dominant pair (parents) breed (Kilham 1989). Some breeding concentrations may reach 0.8 pairs/ha (Auk 109:609-612).

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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: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization

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)

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Corvus brachyrhynchos

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 6 barcode sequences available from BOLD and GenBank.

Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

ACCGCCCTA---AGCCTCCTCATCCGAGCAGAACTAGGCCAACCAGGCGCTCTGCTAGGAGAC---GATCAAATCTATAATGTAATCGTTACAGCTCATGCCTTTGTCATAATCTTCTTTATAGTAATGCCAATCATAATCGGAGGATTTGGAAACTGACTAGTCCCTCTAATG---ATTGGTGCCCCAGANATAGCATTCCCACGAATAAACAACATAAGCTTCTGACTCCTCCCACCCTCCTTCCTTCTCCTTCTAGCCTCTTCCACAGTAGAAGCAGGAGCAGGAACAGGATGAACCGTGTACCCGCCACTAGCTGGCAACCTAGCCCACGCTGGAGCCTCAGTCGACCTA---GCCATCTTCTCGCTACATCTAGCAGGTATCTCCTCCATCCTAGGGGCAATTAACTTCATCACCACAGCAATTAACATAAAACCCCCAGCCCTCTCACAATACCAAACCCCTCTGTTCGTATGATCCGTACTAATTACCGCAGTACTACTCCTTCTCTCCCTACCTGTACTTGCTGCC---GGAATTACTATGCTTCTAACAGACCGTAACCTCAACACCACATTCTTCGATCCAGCAGGAGGAGGAGACCCAGTACTATACCAACACCTA------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------TTC
-- end --

Download FASTA File

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Statistics of barcoding coverage: Corvus brachyrhynchos

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 9
Specimens with Barcodes: 12
Species With Barcodes: 1
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Conservation

Conservation Status

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

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s

Justification
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding

United States

Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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American crows are thriving, particularly in association with suburban areas. Their numbers may be increasing.

IUCN Red List of Threatened Species: least concern

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

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Population

Population Trend
Increasing
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Relevance to Humans and Ecosystems

Benefits

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

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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

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Economic Importance for Humans: Negative

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

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Economic Importance for Humans: Positive

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

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Wikipedia

American crow

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. In the interior of the continent south of the Arctic, it is referred to as simply the "crow".

It is one of several species of corvid that are entirely black, though it can be distinguished from the other two such birds in its range—from the common raven (C. corax) by size and behavior and from the fish crow (C. ossifragus) by call (but see below). It is also distinguished from the raven by its smaller bill.[citation needed]

American crows are common, widespread and adaptable, but they are highly susceptible to the West Nile virus. They are monitored as a bioindicator. Direct transmission of the virus from American crows to humans is not recorded to date, and in any case not considered likely.

Although the American crow and the Hooded crow are very similar in size, structure and behavior, their calls are different. The American crow nevertheless occupies the same role the Hooded crow does in Eurasia.

Taxonomy[edit]

The American crow was described by Christian Ludwig Brehm in 1822.[2] Its scientific name means literally "short-billed crow", from Ancient Greek brachy- (βραχυ-) "short-" and rhynchos (ρυνχος) "billed".[3]

The northwestern crow (C. caurinus) is very closely related to the American crow. Its ancestors became separated by Ice Age glaciation west of the Rocky Mountains. It is endemic to Pacific temperate rain forests where it all but replaces the American crow. Only in the Seattle region do they co-occur to any extent. In form the two species are much alike. There is a marked difference in voice.[4]

Subspecies[edit]

Four subspecies are recognized. They 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 south coast.[5]

Description[edit]


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An American crow calling
The skull of an American crow

The American crow is a 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).[5] The body mass can vary from 316 to 620 g (11.1 to 21.9 oz). Males tend to be larger than females.[8][9]

Brooklyn Museum - American crow - John J. Audubon

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.

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 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, their larger-looking heads and of course their strongly solitary habits. They also fluff their throat feathers when calling like fish crows, only more so.[10]

The average life span of the American crow in the wild is 7–8 years. Captive birds are known to have lived up to 30 years.[11]

Distribution and habitat[edit]

The range of the American crow 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] Virtually all types of country from wilderness, farmland, parks, open woodland to towns and major cities are inhabited; it is absent only from Pacific temperate rain forests and tundra habitat where it is replaced by the raven. This crow is a permanent resident in most of the USA, 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[12]) communal roosts at night.

The American crow was recorded in Bermuda from 1876 onwards.[13]

Behavior[edit]

Diet[edit]

The American crow is omnivorous. It will feed on invertebrates of all types, 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. Occasionally, they will visit bird feeders.[14] The American crow is one of only a few species of bird that has been observed modifying and using tools to obtain food.[15]

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.[14]

Reproduction[edit]

An American crow egg, in the collection of the Children's Museum of Indianapolis

American crows are monogamous cooperative breeding birds. Mated pairs form large families of up to 15 individuals from several breeding seasons that remain together for many years.[16] 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.[10][17] Most do not leave the nest to breed for four to five years.[16]

The nesting season starts early, with some birds incubating eggs by early April.[18] 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 35 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.[14][19]

West Nile virus[edit]

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.[20] Despite this decline, the crow is considered a species of least concern.[21] 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.[17][22] 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.[11]

Status and conservation[edit]

Crows have been killed in large numbers by humans, both for recreation and as part of organized campaigns of extermination.[23]

American crows are protected internationally by the Migratory Bird Treaty Act of 1918. Despite attempts by humans in some areas to drive away or eliminate these birds, they remain widespread and very common. The number of individual American crows is estimated by BirdLife International to be around 31,000,000. The large population, as well as its vast range, are the reasons why the American crow is considered to be of least concern, meaning that the species is not threatened.[1]

References[edit]

  1. ^ a b c BirdLife International (2012). "Corvus brachyrhynchos". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ Corvus brachyrhynchos. Wikispecies
  3. ^ Liddell, Henry George; Scott, Robert; Stuart-Jones, Henry and McKenzie, Roderick: (1980): A Greek-English Lexicon (abridged ed.). Oxford University Press, Oxford, UK. ISBN 0-19-910207-4.
  4. ^ Dick, Gary Owen (2007): American Crow. Whatbird.com – Field Guide to Birds of North America. identify.whatbird.com/obj/103/_/American_Crow.aspx Retrieved 2007-October-18.
  5. ^ a b Madge, Steve & Burn, Hilary (1994): Crows and jays: a guide to the crows, jays and magpies of the world. A&C Black, London. ISBN 0-7136-3999-7.
  6. ^ a b Goodwin & Gillmor (1976): p. 87
  7. ^ Goodwin & Gillmor (1976) p. 88.
  8. ^ Kilham, Lawrence. The American Crow and the Common Raven. p. 52
  9. ^ American Crow, Life History, All About Birds – Cornell Lab of Ornithology. Allaboutbirds.org. Retrieved on 2013-03-06.
  10. ^ a b Seattle Audubon Society: BirdWeb – American Crow. Retrieved 2006-October-24.
  11. ^ a b Connecticut Department of Environmental Protection (2001): American Crow Fact Sheet. Version of 2001. Retrieved 2006-October-25.
  12. ^ Di Dilvestro, Roger. "Something To Crow About". National Wildlife Federation. 
  13. ^ Long, John L. (1981). Introduced Birds of the World: The worldwide history, distribution and influence of birds introduced to new environments. Terrey Hills, Sydney: Reed. p. 354. ISBN 0-589-50260-3. 
  14. ^ a b c Parr, C. (2005): Animal Diversity WebCorvus brachyrhynchos. Retrieved 2007-October-24.
  15. ^ Caffrey, Carolee (2000). "Tool Modification and Use by an American Crow". Wilson Bull. 112 (2): 283–284. doi:10.1676/0043-5643(2000)112[0283:TMAUBA]2.0.CO;2. 
  16. ^ a b Roger Segelken: Tree-climbing researcher knows exactly how far the crow flies Cornell Chronicle. Retrieved 2006-October-25,
  17. ^ a b Cornell Lab of Ornithology (2002): Bird Guide – American Crow. Retrieved 2006-October-24.
  18. ^ Henninger, W.F. (1906). "A preliminary list of the birds of Seneca County, Ohio". Wilson Bulletin 18 (2): 47–60. 
  19. ^ Johnson, Ron American Crows. Internet Center for Wildlife Damage Management
  20. ^ LaDeau, Shannon L.; Kilpatrick, A. Marm; Marra, Peter P. (2007). "West Nile virus emergence and large-scale declines of North American bird populations". Nature 447 (7145): 710–713. doi:10.1038/nature05829. PMID 17507930. 
  21. ^ Deen, David (December 12, 2012). "The crow – a sociable bird with a long memory". The Chronicle (Barton, Vermont). p. 34. 
  22. ^ Caffrey, Carolee; Smith, Shauna C.R. & Weston, Tiffany J. (2005). "West Nile Virus Devastates an American Crow Population". Condor 107 (1): 128–132. doi:10.1650/7646. 
  23. ^ Campbell, Robert Wayne & Canadian Wildlife Service (1997). "American Crow". The Birds of British Columbia: Passerines : flycatchers through vireos. UBC Press. p. 227. ISBN 978-0-7748-0572-8. 

Bibliography[edit]

  • Goodwin, Derek & Gillmor, Robert (1976): Crows of the World (1st ed.). University of Washington Press, Seattle.
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Names and Taxonomy

Taxonomy

Comments: Considered conspecific with and constitutes a superspecies with C. CAURINUS (AOU 1998). Considered to be closely related to or conspecific with C. CORONE by some authors, but this seems unlikely (AOU 1998).

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