American crow
American crow | |
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In Bruce Peninsula National Park, Ontario | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Corvidae |
Genus: | Corvus |
Species: | C. brachyrhynchos
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Binomial name | |
Corvus brachyrhynchos Brehm, 1822
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Global range |
The American crow (Corvus brachyrhynchos) is a large
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
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
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
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
- C. b. brachyrhynchos (nominate subspecies, and largest.
- C. b. hesperis (Ridgway, 1887) – western crow: western North America except the Arctic north, the Pacific Northwest and the extreme south. Smaller overall with a proportionally more slender bill[7] and low-pitched voice.
- C. b. caurinus (Pacific temperate rain forests was formerly considered a distinct species as C. caurinus, averaging smaller in size than other American crows with a distinctly hoarser call.[8] It forms a hybrid swarm with American crow (sensu stricto) in coastal Washington and British Columbia.[9] The American Ornithological Society lumped the northwestern crow with the American crow in 2020.[10] It is now considered a geographic variation within C. b. hesperis.[11]
- C. b. pascuus (Coues, 1899) – Florida crow: Florida. Mid-sized, short-winged, but decidedly long bill and legs.[7]
- C. b. paulus (Howell, 1913) – southern crow: southern United States. Smaller overall, bill also small.[12]
Description
The American crow is a large, distinctive bird with iridescent black feathers all over. Its legs, feet and bill are also black. They measure 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]
Distribution and habitat
The range of the American crow now extends from the
The American crow was recorded in
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
The American crow is
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
American crows are socially
The nesting season starts early, with some birds incubating eggs by early April.
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
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
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
Status and management
The intelligence and adaptability of the American crow has insulated it from threats, and it is instead considered an agricultural pest.
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
- ^ . Retrieved 19 November 2021.
- ^ S2CID 241865621.
- ISBN 0-19-910207-4.
- PMID 22642364.
- ^ 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.
- ^ ISBN 0-7136-3999-7.
- ^ a b Goodwin & Gillmor (1976): p. 87
- ^ 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.
- S2CID 211064373.
- ISSN 0004-8038.
- ^ "Corvus brachyrhynchos hesperis (caurinus or occidentalis) (American Crow (caurinus or occidentalis)) – Avibase". avibase.bsc-eoc.org. Retrieved 2021-10-19.
- ^ Goodwin & Gillmor (1976) p. 88.
- ^ Kilham, Lawrence. The American Crow and the Common Raven. p. 52
- ^ American Crow, Life History, All About Birds – Cornell Lab of Ornithology. Allaboutbirds.org. Retrieved on 2013-03-06.
- ISBN 978-0-89096-466-8.
- ^ 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.
- ^ "Differences Between an American Crow and a Common Raven (with Map, Pictures, and Sounds)". Avian Report. 22 July 2020. Retrieved June 2, 2023.
- ^ Mayntz, Melissa (April 13, 2021). "Raven or Crow: Learn to Identify Both". The Spruce. Retrieved June 2, 2023.
- ^ Amanda Heidt. "Like humans, these big-brained birds may owe their smarts to long childhoods".
- ^ Chris Baraniuk. "Crows have long been considered cunning. But their intelligence may be far more advanced than we ever thought possible".
- ^ 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.
- ^ Houston S. 1977. Changing patterns of Corvidae on the prairies. Blue Jay 35:149–155.
- ^ Livezey KB. 2009a. Range expansion of Barred Owls, part I: chronology and distribution. American Midland Naturalist 161:49–56.
- ^ Livezey KB. 2009b. Range expansion of Barred Owls, part 2: facilitating ecological changes. American Midland Naturalist 161:323–349.
- ^ Livezey KB. 2010. Killing barred owls to help spotted owls II: implications for many other range-expanding species. Northwestern Naturalist 91:251–270.
- ^ Di Dilvestro, Roger. "Something To Crow About". National Wildlife Federation.
- JSTOR 4089282.
- ISBN 0-589-50260-3.
- ^ a b "Corvus brachyrhynchos (American crow)". Animal Diversity Web.
- ^ a b c C. Parr (2005). "Corvus brachyrhynchos". Animal Diversity Web. Retrieved 13 September 2015.
- S2CID 86124230.
- ^ 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,
- ^ a b Cornell Lab of Ornithology (2002): Bird Guide – American Crow. Retrieved 2006-October-24.
- Wilson Bulletin. 18 (2): 47–60.
- ^ Johnson, Ron American Crows Archived 2017-07-16 at the Wayback Machine. Internet Center for Wildlife Damage Management
- S2CID 4337661.
- ^ Deen, David (December 12, 2012). "The crow – a sociable bird with a long memory". The Chronicle. Barton, Vermont. p. 34.
- S2CID 85419982.
- S2CID 86124230.
- ^ a b Sullivan, Emily. "The Glorious American Crow - Romanticism at SU". Archived from the original on 2020-09-28. Retrieved 2021-10-23.
- ^ "Crow Symbolism & Meaning (+Totem, Spirit & Omens)". CBS 19 News. Retrieved 26 February 2023.
- ISBN 978-0-7748-0572-8.
Bibliography
- Goodwin, Derek & Gillmor, Robert (1976): Crows of the World (1st ed.). University of Washington Press, Seattle.
External links
- Skull of American Crow
- Pictures of American Crow on Birds of the World at Flickr
- "American Crow media". Internet Bird Collection.
- "American crow" at the Encyclopedia of Life
- American Crow call
- American Crow photo gallery at VIREO (Drexel University)
- Northwestern Crow call (two birds)