Corvus brachyrhynchos Brehm, 1822

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American Crow
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Subclass: Neornithes
Infraclass: Neognathae
Superorder: Neoaves
Order: Passeriformes
Suborder: Passeri
Superfamily: Corvoidea
Family: Corvidae
Genus: Corvus
Species: C. brachyrhynchos
Binomial name
Corvus brachyrhynchos
Brehm, 1822
Global range
Profile of a crow

Note: This is part of a set of demo pages for potential contributions that are single publication like articles rather than database entries. This first page shows material from the animal diversity web (authored by C. Parr, all cited) and adds later material from Wikipedia (both reused under cc-by-sa 3.0, see first version of this document for author attribution).

The points this demo page is trying to make are:

  1. Typical EoL material can be easily harvested based on the headings (compare the corresponding EoL page).
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  4. The mediawiki technology is flexible and can markup more granular information than sections of text. Already in "Reproduction" the start and end of breeding season and longevity (an SPM concept!) have been semantically marked up; see the comment at the end of the section.

A second demo page shows the contributions by Parr as authored material, see Corvus brachyrhynchos (by C. Parr)

  • The point of that page is that the mediawiki technology is not limited to Wikipedia-like, mass authored pages, but can be an attractive publication venue, with full and dedicated attribution.

Description

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.[1]

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.[1]

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.[1]

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.[1]

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.[1]

The oldest recorded age of a wild American crow is 14 years and 7 months.

Internal note on information above: Without creating a new paragraph or heading, some information was marked as belonging to a specific semantic category (BreedingStartMonth, BreedingEndMonth, Longevity_verbatim). The red color is for demoing purposes only, normally it would be invisible. Note the tooltip displayed when the mouse hovers. This technology could be further supported through javascript, removing any need to learn markup codes.

Behavior

American crows have an unusual social system - they are cooperative breeders. This means that they may stay close to the place where they were born to help raise young and defend the area against predators. It is not well understood why these offspring do not obtain mates and raise their own families, but pairs with such helpers do not appear to be more successful at fledging offspring than those without helpers. Family members often preen each other (allopreening).[1]

Most American crows defend large all-purpose territories. All members of the family assist in chasing predators away from the territory. Some individuals may remain on their territories during the winter, even if they participate in winter roosts or large flocks searching for food. Winter roosting behavior begins in autumn and peaks in mid-winter. Large numbers of crows, from tens to hundreds of thousands, will assemble in the late afternoon hours in an area with large trees. Often the flock will move from this area to a final roosting area at nightfall.[1]

Some American crows migrate. Researchers have found marked crows from southeastern Michigan as far south as Tennessee, but more often migrants go shorter distances.[1]

In addition to family groups and winter roosts, crows may join a third kind of social group called a floater flock. During the breeding season, floater flocks of up to 50 birds have been observed. Flock participants probably lack mates; at least some of these individuals also spend time on their natal territories as helpers. American crow floater flocks have not been well studied but in other species they allow individuals to roam an area finding mates or vacant territories while staying safely in a group.[1]

American crows engage in a fascinating behavior called anting. A crow will position itself over an anthill and allow ants to scramble among its feathers, or it may pick up an ant and smear its feathers with it.[1]

American crows are considered among the most intelligent birds, though there is little scientific evidence to prove this. American crows are resourceful in their food habits and are extremely difficult for researchers to capture in traps.[1]

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.[1]

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.[1]

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.[1]

Ecology and Distribution

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.[1]

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.[1]

Predation

Crows will group together to vocally harass and chase predators. This behavior is called mobbing.[1]

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.[1]

Trophic Strategy

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.[1]

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.[1]

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.[1]

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.[1]

Conservation Status

American crows are thriving, particularly in association with suburban areas. Their numbers may be increasing.[1]

Uses

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.[1]

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.[1]

Common Names

Name Language
Американска врана Bulgarian - български език
American Crow English - English
corneille d'Amérique French - français
アメリカガラス Japanese - 日本語
Corvo-americano Portuguese - Português
Cuervo americano Spanish - español

NOTE: Although for demonstration purposes, this has the content structure of an eol page it is not meant to replace one, but rather act as an authored data source for the aggregation. It shall demonstrate that in a consistent document structured manner information can be authored as well as aggregated (see Rod Pages demonstrations).Topics such as biodiversity heritage library, gene sequences and barcodes would be automatically added using portlets.

The following paragraphs are from Wikipedia. Some of them could be merged with above, some represent aspects that EoL may not be interested in. Source: http://en.wikipedia.org/wiki/American_Crow, copied under cc-by-sa licence on 14. Nov. 2009, with attribution to authors in the first version of this page, see history):

Introduction (Start of Wikipedia material)

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 simply "the crow" as no other such birds occur there on any regular basis.

It is one of several species of corvid which are entirely black in color, though it can be distinguished from the other two (but see also below) such birds in its range - from the Common Raven (C. corax) by size and behavior, and on the East Coast of the United States from the Fish Crow (C. ossifragus) by call.

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.

Taxonomy

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

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 by and large endemic to Pacific temperate rain forests where it all but replaces the American Crow. Only in the Seattle region they co-occur to any extent. In habitus, they are still much alike to each other from one another where their ranges overlap. The voice however represents a distinct difference between the two species.[3]

Subspecies

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.[4]

  • Corvus brachyrhynchos brachyrhynchos: Northeastern United States, eastern Canada and surroundings. Largest subspecies.
  • Corvus brachyrhynchos hesperis – Western Crow: Western North America except arctic north, Pacific Northwest and extreme south. Smaller overall with a proportionally more slender bill[5] and low-pitched voice.
  • Corvus brachyrhynchos pascuus – Florida Crow: Florida. Mid-sized, short-winged but decidedly long bill and legs.[5]
  • Corvus brachyrhynchos paulus: Southern United States. Smaller overall, bill also small.[6]

Description

"Caah-caah-caah"
American Crow calls
Problems listening to this file? See media help.

The American Crow is a distinctive bird with iridescent black feathers all over. Its legs, feet and bill are also black. They are 40–50 centimeters (16–20 in) in length, of which the tail makes up about 40%. Each wing is around 27–34 centimeters (7–8 in) long. The bill length is on average 5 centimeters (2 in), varying strongly according to location.[4]

The most usual call is a loud, short, and rapid caah-caah-caah. 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.[7]

Most wild American Crows live for about 7–8 years. Captive birds are known to have lived up to 30 years.[8]

Distribution and habitat

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.[9] 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. 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 communal roosts at night.

The American Crow was recorded in Bermuda from 1876 onwards.[10]

Behavior

Diet

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.[11] The American Crow is one of only a few species of bird that has been observed modifying and using tools to obtain food.[12]

Like most crows, they will scavenge at landfills, scattering garbage in the process. Where available, maize, 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.[11]

Silhouette of an American Crow.

Reproduction

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.[13] 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.[14] Most do not leave the nest to breed for four to five years.[13]

The nesting season starts early, with some birds incubating eggs by early April.[15] American Crows build bulky stick nest, 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.

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;[16] 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] 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.[8]

Status and conservation

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.[9]

In popular culture

The abundance of the American Crow in both rural and urban environments have made them very familiar to all Americans. They are the archetypal "crow" of North America and have found their way to vernacular speech and popular culture.

  • "Eating crow" means suffering embarrassment after having previously boasted. This phrase originates in the use of crows - including this species - as famine food (compare "humble pie"). While American Crows are theoretically edible they have little meat; in addition, those from densely-settled areas often carry parasites that can infect humans.
  • In the early 20th century, "crow" was common as a racial slur for African Americans. For example, the White American vaudeville act Moran and Mack had a performance called "Two Black Crows" which was popular in the 1920s, where they played two stereotyped "crows" speaking in exaggerated Black American accents.
  • "Jim Crow" was originally the name of a 19th-century minstrel character. It became a collective term for blackface performances of that era, as well as laws - particularly in the American South - that segregated blacks.
  • The comic book series The Crow by James O'Barr features a supernatural American Crow that resurrects the protagonist, Eric Draven, as an undead vigilante.

Footnotes

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 Parr, Cynthia Sims 2005. "Corvus brachyrhynchos" (On-line), Animal Diversity Web. Accessed October 25, 2009 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Corvus_brachyrhynchos.html.
  2. ↑ Liddell et al. (1980)
  3. ↑ Dick (2007)
  4. ↑ 4.0 4.1 Madge & Burn (1994)
  5. ↑ 5.0 5.1 Goodwin & Gillmor (1976): p.87
  6. ↑ Goodwin & Gillmor (1976): p.88
  7. ↑ BirdWeb (2005)
  8. ↑ 8.0 8.1 CDEP (2001)
  9. ↑ 9.0 9.1 BLI (2004)
  10. ↑ 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. 
  11. ↑ 11.0 11.1 Parr (2005)
  12. ↑ Caffrey (2000)
  13. ↑ 13.0 13.1 Roger Segelken: Tree-climbing researcher knows exactly how far the crow flies Cornell Chronicle. Retrieved 2006-OCT-25,
  14. ↑ CLO (2002), SAS (2005)
  15. ↑ Henninger (1906)
  16. ↑ LaDeau, Shannon L.; A. Marm Kilpatrick; Peter P. Marra (2007-06-07). "West Nile virus emergence and large-scale declines of North American bird populations". Nature 447: 710-713. doi:10.1038/nature05829. http://www.nature.com/nature/journal/v447/n7145/abs/nature05829.html. 
  17. ↑ CLO (2002), Caffrey et al. 2005)

References

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Title: Wikinomics
Creator: Don Tapscott
Date: 2006-10-01

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