American crow

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American crow
In Bruce Peninsula National Park, Ontario

Least Concern (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Corvidae
Genus: Corvus
Species:
C. brachyrhynchos
Binomial name
Corvus brachyrhynchos
Brehm, 1822
Global range
Pair of crows chasing away a red-tailed hawk from their nest

The American crow (Corvus brachyrhynchos) is a large

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. Its wingspan is 85–100 cm (33–39 in). 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.

Taxonomy and systematics

The American crow was described by German ornithologist

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]

Subspecies

Northwestern crow range

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]

Description

An American crow making its distinctive call.
American crow - Brooklyn, New York
The skull of an American crow

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]

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, 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]

Bird on a human's hand
A fledgling, of the Northwestern subtype

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]

Distribution and habitat

The range of the American crow now extends from the

nesting season these birds often gather in large (thousands or even millions[26]) communal roosts at night.[27]

The American crow was recorded in

Bermuda from 1876 onwards.[28]

Behavior and ecology

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.[2]

Diet

American crow skeleton (Museum of Osteology)

The American crow is

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]

Reproduction

Children's Museum of Indianapolis

American crows are socially

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.

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]

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, 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

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]

Intelligence

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]

Relationship with humans

Crows are used as a motif in some human cultures, 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]

Status and management

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

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.

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]

References

  1. ^ . Retrieved 19 November 2021.
  2. ^ .
  3. .
  4. .
  5. ^ Gill, Frank; Donsker, David, eds. (2021). "Crows, mudnesters, melampittas, Ifrit, birds-of-paradise". World Bird List Version 11.2. International Ornithologists' Union. Retrieved 26 October 2021.
  6. ^ .
  7. ^ a b Goodwin & Gillmor (1976): p. 87
  8. ^ 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.
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  11. ^ "Corvus brachyrhynchos hesperis (caurinus or occidentalis) (American Crow (caurinus or occidentalis)) – Avibase". avibase.bsc-eoc.org. Retrieved 2021-10-19.
  12. ^ Goodwin & Gillmor (1976) p. 88.
  13. ^ Kilham, Lawrence. The American Crow and the Common Raven. p. 52
  14. ^ American Crow, Life History, All About Birds – Cornell Lab of Ornithology. Allaboutbirds.org. Retrieved on 2013-03-06.
  15. .
  16. ^ McGowan, Kevin (April 6, 2005). "How do you tell a Fish Crow Corvus ossifragus from an American Crow Corvus brachyrhynchos?". cornell.edu. Retrieved June 2, 2023.
  17. ^ "Differences Between an American Crow and a Common Raven (with Map, Pictures, and Sounds)". Avian Report. 22 July 2020. Retrieved June 2, 2023.
  18. ^ Mayntz, Melissa (April 13, 2021). "Raven or Crow: Learn to Identify Both". The Spruce. Retrieved June 2, 2023.
  19. ^ Amanda Heidt. "Like humans, these big-brained birds may owe their smarts to long childhoods".
  20. ^ Chris Baraniuk. "Crows have long been considered cunning. But their intelligence may be far more advanced than we ever thought possible".
  21. ^ a b Connecticut Department of Environmental Protection (2001): American Crow Fact Sheet Archived November 5, 2006, at the Wayback Machine. Version of 2001. Retrieved 2006-October-25.
  22. ^ Houston S. 1977. Changing patterns of Corvidae on the prairies. Blue Jay 35:149–155.
  23. ^ Livezey KB. 2009a. Range expansion of Barred Owls, part I: chronology and distribution. American Midland Naturalist 161:49–56.
  24. ^ Livezey KB. 2009b. Range expansion of Barred Owls, part 2: facilitating ecological changes. American Midland Naturalist 161:323–349.
  25. ^ Livezey KB. 2010. Killing barred owls to help spotted owls II: implications for many other range-expanding species. Northwestern Naturalist 91:251–270.
  26. ^ Di Dilvestro, Roger. "Something To Crow About". National Wildlife Federation.
  27. JSTOR 4089282
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  28. .
  29. ^ a b "Corvus brachyrhynchos (American crow)". Animal Diversity Web.
  30. ^ a b c C. Parr (2005). "Corvus brachyrhynchos". Animal Diversity Web. Retrieved 13 September 2015.
  31. S2CID 86124230
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  32. ^ a b Roger Segelken: Tree-climbing researcher knows exactly how far the crow flies Archived September 16, 2006, at the Wayback Machine Cornell Chronicle. Retrieved 2006-October-25,
  33. ^ a b Cornell Lab of Ornithology (2002): Bird Guide – American Crow. Retrieved 2006-October-24.
  34. Wilson Bulletin
    . 18 (2): 47–60.
  35. ^ Johnson, Ron American Crows Archived 2017-07-16 at the Wayback Machine. Internet Center for Wildlife Damage Management
  36. S2CID 4337661
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  37. ^ Deen, David (December 12, 2012). "The crow – a sociable bird with a long memory". The Chronicle. Barton, Vermont. p. 34.
  38. S2CID 85419982
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  39. .
  40. ^ a b Sullivan, Emily. "The Glorious American Crow - Romanticism at SU". Archived from the original on 2020-09-28. Retrieved 2021-10-23.
  41. ^ "Crow Symbolism & Meaning (+Totem, Spirit & Omens)". CBS 19 News. Retrieved 26 February 2023.
  42. .

Bibliography

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

External links