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The true crows are large passerine birds that form the genus Corvus in the family Corvidae. Ranging in size from the relatively small pigeon-sized jackdaws (Eurasian and Daurian) to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopiamarker, the 40 or so members of this genus occur on all temperate continents (except South America) and several offshore and oceanic islands (including Hawaiimarker). In the United Statesmarker, the word "crow" is used to refer to the American Crow.The crow genus makes up a third of the species in the Corvidae family. Other corvids include rook and jays. Crows appear to have evolved in Asia from the corvid stock, which had evolved in Australia. A group of crows is called a "murder," though this term usually appears in poetry or similar literature rather than ordinary usage.

Systematics

The genus was originally described by Linnaeus in his 18th century work Systema Naturae. The name is derived from the Latin corvus meaning "raven".The type species is the Common Raven (Corvus corax); others named in the same work include the Carrion Crow (C. corone), the Hooded Crow (C. cornix), the Rook (C. frugilegus), and the Jackdaw (C. monedula).

There is no good systematic approach to the genus at present. Generally, it is assumed that the species from a geographical area are more closely related to each other than to other lineages, but this is not necessarily correct. For example, while the Carrion/Collared/House Crow complex is certainly closely related to each other, the situation is not at all clear regarding the Australian/Melanesian species. Furthermore, as many species are similar in appearance, determining actual range and characteristics can be very difficult, such as in Australia where the five (possibly six) species are almost identical in appearance.

The fossil record of crows is rather dense in Europe, but the relationships among most prehistoric species is not clear. Jackdaw-, crow- and raven-sized forms seem to have existed since long ago and crows were regularly hunted by humans up to the Iron Age, documenting the evolution of the modern taxa. American crows are not as well-documented.

A surprisingly high number of species have become extinct after human colonization, especially of island groups such as New Zealand, Hawaii and Greenland.

Species

Living and recently extinct species


  • Species name - Common Names (range)
    • Subspecies...
  • Corvus alberculos - White-necked Raven or Cape Raven (Southern, central and eastern Africa)
  • Corvus albus - Pied Crow (Central African coasts to southern Africa)
  • Corvus bennetti - Little Crow (Australia)
  • Corvus brachyrhynchos - American Crow (North America, southern Canada, northern Mexico)
  • Corvus capensis - Cape Crow or Black Crow or Cape Rook (Eastern and southern Africa)
  • Corvus caurinus - Northwestern Crow (Olympic peninsula to southwest Alaska)
  • Corvus corax - Common Raven or Northern Raven (The Holarctic south throughout middle Europe, Asia, and North America to Nicaragua)
    • Corvus (corax) sinuatus - Western Raven (Holarctic; Arctic, North America, Eurasia, northern Africa, Pacific islands and British Isles)
    • Corvus (corax) varius morpha leucophaeus - Pied Raven an extinct color variant (Holarctic)
  • Corvus corone - Carrion Crow or Eurasian Crow (Western Europe from British Isles to Germany, eastern Asia)
    • Corvus (corone) capellanus - Mesopotamian Crow or Iraq Pied Crow (Southern Iraq to extreme southwest Iran)
    • Corvus (corone) cornix - Hooded Crow (Northern and western Europe through Turkey, but only North Western Scotland and Northern Ireland in the United Kingdom as the Carrion Crow is more common on most of the British mainland; Syria, Iran, Iraq)
    • Corvus (corone) orientalis - Eastern Carrion Crow (Eurasia and northern Africa)
  • Corvus coronoides - Australian Raven (Eastern and southern Australia)
  • Corvus crassirostris - Thick-billed Raven (Ethiopia)
  • Corvus cryptoleucus - Chihuahuan Raven (Southwestern U.S., northwestern Mexico)
  • Corvus dauuricus - Daurian Jackdaw (Eastern Europe to eastern Japan, occasionally Scandinavia)
  • Corvus enca - Slender-billed Crow (Malaysia, Borneo, Indonesia)
    • Corvus (enca) violaceus - Violaceous Crow (Philippines, Ceram, Moluccas)
  • Corvus florensis - Flores Crow (Flores Island)
  • Corvus frugilegus - Rook (Europe, Asia, New Zealand)
  • Corvus fuscicapillus - Brown-headed Crow (New Guinea)
  • Corvus hawaiiensis (formerly C. tropicus) - Hawaiian Crow or 'Alala (Island of Hawaii)
  • Corvus imparatus - Tamaulipas Crow (Gulf of Mexico coast from Nuevo Leon east to Rio Grande delta, south to Tampico, Tamaulipas)
  • Corvus jamaicensis - Jamaican Crow (Jamaica)
  • Corvus kubaryi - Mariana Crow or Aga (Guam, Rota)
  • Corvus leucognaphalus - White-necked Crow (Haiti, Dominica, Puerto Rico)
  • Corvus macrorhynchos - Large-billed Crow (Eastern Asia, Himalayas, Philippines)
    • Corvus (macrorhynchos) levaillantii - Jungle Crow (India, Burma)
  • Corvus meeki - Bougainville Crow or Soloman Islands Crow (Northern Soloman Islands)
  • Corvus mellori - Little Raven (Southeastern Australia)
  • Corvus monedula - Jackdaw or Western Jackdaw (British Isles and western Europe, Scandinavia, northern Asia, Northern Africa)
  • Corvus moneduloides - New Caledonian Crow (New Caledonia, Loyalty Islands)
  • Corvus nasicus - Cuban Crow (Cuba, Isla de la Juventud, Grand Caicos Island)
  • Corvus orru - Torresian Crow or Australian Crow (Australia, New Guinea and nearby islands)
  • Corvus ossifragus - Fish Crow (Eastern U.S. coast, southeastern U.S. through Florida, west along major rivers to Oklahoma and Texas)
  • Corvus palmarum - Palm Crow (Cuba, Haiti, Dominica)
  • Corvus rhipidurus - Fan-tailed Raven (Northeast Africa, Middle East)
  • Corvus ruficolis - Brown-necked Raven or Desert Raven (Northern Africa, Arabia, southeast to eastern Asia)
    • Corvus (ruficolis) edithae - Somali Crow or Dwarf Raven (Northeast Africa)
  • Corvus sinaloae - Sinaloan Crow (Pacific coast from Sonora to Colima)
  • Corvus splendens - House Crow or Indian House Crow (Indian subcontinent, Middle East, east Africa)
  • Corvus tasmanicus - Forest Raven or Tasmanian Raven (Tasmania and adjacent south coast of Australia)
    • Corvus (tasmanicus) boreus - Relict Raven (Northeastern New South Wales)
  • Corvus torquatus - Collared Crow (Eastern China, south into Vietnam)
  • Corvus tristis - Grey Crow or Bare-faced Crow (New Guinea and neighboring islands)
  • Corvus typicus - Piping Crow or Celebes Pied Crow (Sulawesi, Muna, Butung)
  • Corvus unicolor - Banggai Crow (Banggai Island) - possibly extinct
  • Corvus validus - Long-billed Crow (Northern Moluccas)
  • Corvus woodfordi - White-billed Crow or Soloman Islands Crow (Southern Soloman Islands)
List sources

Prehistoric and fossilized species

In addition to the prehistoric forms listed above, some extinct chronosubspecies have been described. These are featured under the respective species accounts.

Crows and humans

Certain species have been considered pests; the Common Raven, Australian Raven and Carrion Crow have all been known to kill weak lambs as well as eating freshly dead corpses probably killed by other means. Rooks have been blamed for eating grain in the UK and Brown-necked Raven for raiding date crops in desert countries.

In Auburn, New York (USA), 25,000 to 50,000 American Crows (C. brachyrhynchos) have taken to roosting in the small city's large trees during winter since around 1993. In 2003, a controversial, organized crow hunt proved ineffective at reducing their numbers and the problem (concerns for public health and the sheer noise of so many crows) continues.

At a Technology Entertainment Design conference in March 2008, Joshua Klein presented the potential use of a vending machine for crows. He suggested the crows could be trained to pick up trash and the vending machine would be designed to give a reward in exchange for the trash.

Crows have also been known to imitate the human voice, just like parrots. Crows that have been trained to "speak" are considered valuable in parts of East Asia, as crows are a sign of luck.

Some people have adopted crows as pets.

Though humans cannot generally tell individual crows apart, crows have been shown to have the ability to visually recognize individual humans, and to transmit information about "bad" humans by squawking.

Hunting

In the United States it is legal to hunt crows in all states usually from around August to the end of March and anytime if they are causing a nuisance or health hazard. There is no bag limit when taken during the "crow hunting season." According to the US Code of Federal Regulations, crows may be taken without a permit in certain circumstances. USFWS 50 CFR 21.43 (Depredation order for blackbirds, cowbirds, grackles, crows and magpies) states that a Federal permit is not required to control these birds "when found committing or about to commit depredations upon ornamental or shade trees, agricultural crops, livestock, or wildlife, or when concentrated in such numbers and manner as to constitute a health hazard or other nuisance," provided
  • that none of the birds killed or their parts are sold or offered for sale,
  • 
    
  • that anyone exercising the privileges granted by this section shall permit any Federal or State game agent free and unrestricted access over the premises where the operations have been or are conducted and will provide them with whatever information required by the officer, and
  • 
    
  • that nothing in the section authorizes the killing of such birds contrary to any State laws and that the person needs to possess whatever permit as may be required by the State.
  • 
    


    In the UK, the crow is considered a pest when in a large community and under certain conditions can be shot under a number of general licenses issued by DEFRAmarker.

    Evolution

    Crows appear to have evolved in central Asia and radiated out into North America, Africa, Europe, and Australia.

    The latest evidence in the crow's evolution indicates descent from the Australasian family Corvidae. However, the branch that would produce the modern groups such as jays, magpies and large predominantly black Corvus had left Australasia and were concentrated in Asia by the time the Corvus evolved. Corvus has since re-entered Australia (relatively recently) and produced five species with one recognized sub-species.

    Behavior

    Calls

    Crows make a wide variety of calls or vocalizations. Whether the crows' system of communication constitutes a language is a topic of debate and study. Crows have also been observed to respond to calls of other species; this behavior is presumably learned because it varies regionally. Crows' vocalizations are complex and poorly understood. Some of the many vocalizations that crows make are a "caw", usually echoed back and forth between birds, a series of "caws" in discrete units, counting out numbers, a long caw followed by a series of short caws (usually made when a bird takes off from a perch), an echo-like "eh-aw" sound, and more. These vocalizations vary by species, and within each species vary regionally. In many species, the pattern and number of the numerical vocalizations have been observed to change in response to events in the surroundings (i.e. arrival or departure of crows). Crows can hear sound frequencies lower than those that humans can hear, which complicates the study of their vocalizations.

    Loud, throaty "caw-aw-ah"'s are usually used to indicate hunger or to mark territory. When defending a nest site or food, crows will usually enlarge their crest feathers and hunch their shoulders to increase their size.Softer, gurgling sounds have also been observed as a sort of beckoning call, or a call of affection. These noises are emitted from within the throat of the bird, much like a cat's purring.

    Intelligence

    As a group, the crows show remarkable examples of intelligence, and Aesop's fable of The Crow and the Pitcher shows that humans have long viewed the crow as an intelligent bird. Crows and ravens often score very highly on intelligence tests. Certain species top the avian IQ scale. Wild hooded crows in Israel have learned to use bread crumbs for bait-fishing. Crows will engage in a kind of mid-air jousting, or air-"chicken" to establish pecking order.

    One species, the New Caledonian Crow, has also been intensively studied recently because of its ability to manufacture and use its own tools in the day-to-day search for food. These tools include 'knives' cut from stiff leaves and stiff stalks of grass. Another skill involves dropping tough nuts into a heavy trafficked street and waiting for a car to crush them open, and then waiting at pedestrian lights with other pedestrians in order to retrieve the nuts. On October 5, 2007, researchers from the University of Oxfordmarker, Englandmarker presented data acquired by mounting tiny video cameras on the tails of New Caledonian Crows. It turned out that they use a larger variety of tools than previously known, plucking, smoothing and bending twigs and grass stems to procure a variety of foodstuffs. Crows in Queenslandmarker, Australia have learned how to eat the toxic cane toad by flipping the cane toad on its back and violently stabbing the throat where the skin is thinner, allowing the crow to access the non-toxic innards; their long beaks ensure that all of the innards can be removed. Recent research suggests that crows have the ability to recognize one individual human from another by facial features.

    Colour and society

    Extra-specific uses of colour in crow societies

    Many crow species are all black. Most of their natural enemies, the raptor or "falconiformes", soar high above the trees, and hunt primarily on bright, sunny days when contrast between light and shadow is greatest. Crows usually hunt in groups of other crows, called murders. Crows take advantage of this by maneuvering themselves through the dappled shades of the trees, where their black color renders them effectively invisible to their enemies above , in order to set up complex ambush attacks . It is perhaps here where we find the greatest difference between ravens and crows—ravens tend to soar high in the air as raptors do. Fledglings are much duller than adults in appearance.

    While hawks tend to be the primary daytime predators of crows, their most deadly predators, in many areas, are the owls that hunt by night . Crows also will often mob owls much more fiercely when they find them in daylight than the hawks and other raptors . Frequently crows appear to "play" with hawks, taking turns "counting coup" while escorting the raptor out of their territory. Their attacks on owls, on the other hand, possess a definite serious quality.

    Intra-specific uses of color in crow societies

    Even in species characterized by being all black, one will still occasionally find variations, most of which appear to result from varying degrees of albinism, such as:

    • an otherwise all-black crow stunningly contrasted by a full set of brilliant, pure-white primary feathers.
    • complete covering in varying shades of grey (generally tending toward the darker side).
    • blue or red, rather than swarthy eyes (blue being more common than red).
    • Some combination of the above


    The treatment of these rare individuals may vary from group to group, even within the same species. For example, one such individual may receive special treatment, attention, or care from the others in its group , while another group of the same species might exile such individuals, forcing them to fend for themselves. The reason for such behaviors may relate to the fact that colorful differences can draw attention from unwanted predators.

    In culture and mythology

    See also Raven in mythology and Cultural depictions of ravens.


    Crows, and especially ravens, often feature in European legends or mythology as portent or harbingers of doom or death, because of their dark plumage, unnerving calls, and tendency to eat carrion. They are commonly thought to circle above scenes of death such as battles.

    In occult circles, distinctions are sometimes made between crows and ravens. In mythology and folklore as a whole, crows tend to be symbolic more of the spiritual aspect of death, or the transition of the spirit into the afterlife, whereas ravens tend more often to be associated with the negative (physical) aspect of death. However, few if any individual mythologies or folklores make such a distinction, and there are ample exceptions. Another reason for this distinction is that while crows are typically highly social animals, ravens don't seem to congregate in large numbers anywhere but:
    1. Near carrion where they meet seemingly by chance, or
    2. At cemeteries, where large numbers sometimes live together, even though carrion there is no more available (and probably less attainable) than any road or field.


    Compendium of Materia Medica states that crows are kind birds that feed their old and weakened parents; this is often cited as a fine example of filial piety.

    In mythology

    A very incomplete list of deities associated with ravens includes the eponymous Pacific Northwest Native figures Raven and Crow, the ravens Hugin and Munin, who accompany the Norse god Odin, the Celtic goddesses the Mórrígan and/or the Badb (sometimes considered separate from Mórrígan), and Shani, a Hindu god who travels astride a crow.

    In the Epic of Gilgamesh, the Chaldean myth, the character Utnapishtim releases a dove and a raven to find land, however, the dove merely circles and returns. Only then does Utnapishtim send forth the raven, who does not return. Utnapishtim extrapolates from this that the raven has found land, which is why it hasn't returned. This would seem to indicate some acknowledgement of crow intelligence, which may have been apparent even in ancient times, and to some might imply that the higher intelligence of crows, when compared to other birds, is striking enough that it was known even then.

    In Buddhism, the Dharmapala (protector of the Dharma) Mahakala is represented by a crow in one of his physical/earthly forms. Avalokiteśvara/Chenrezig, who is reincarnated on Earth as the Dalai Lama, is often closely associated with the crow because it is said that when the first Dalai Lama was born, robbers attacked the family home. The parents fled and were unable to get to the infant Lama in time. When they returned the next morning expecting the worst, they found their home untouched, and a pair of crows were caring for the Dalai Lama. It is believed that crows heralded the birth of the First, Seventh, Eighth, Twelfth and Fourteenth Lamas, the latter being the current Dalai Lama, Tenzin Gyatso.Crows are mentioned often in Buddhism, especially Tibetan disciplines.

    According to Ovid's Metamorphoses, in classical mythology, when the crow told the god Apollo that his lover Coronis was cheating on him with a mortal, he became very angry, and part of that anger was directed at the crow, whose feathers he turned from white to black.

    Myths in India: In Hinduism, it is believed that people who died will take food and offerings through a variety of crows called "Bali kākka". Every year people whose parents or relatives died will offer food to crows as well as cows on the Śrāddha day. A battle between crows and owls is said to have inspired the final bloody night of the Mahabharatha war.

    In Chinese mythology, the world originally had ten suns embodied as ten crows, which rose in the sky one at a time. When all ten decided to rise at once, the effect was devastating to crops, so the gods sent their greatest archer Houyi, who shot down nine crows and spared only one. Having a "crow beak" is a symbolic expression that one is being a jinx.

    In culture

    Literature and film

    The Child ballad The Three Ravens depicts three ravens discussing whether they can eat a dead knight, but finds that his hawk, his hound, and his true love prevent them; in the parody version The Twa Corbies, these guards have already forgotten the dead man, and the ravens can eat their fill. Their depiction of evil has also led to some exaggeration of their appetite. In modern films such as Pirates of the Caribbean: Dead Man's Chest, Damien: Omen II, The Crow and Exorcist: The Beginning, crows are shown tearing out people's eyes while they are still alive. Crows have never been known for this behavior due to their high preference for carrion. Crows are also one of the investigation clues in the ABC TV series FlashForward.And also in CWs Tv series The Vampire Diaries and books, the main character and other characters often see crows around, especially Elena.They add on to the morose mood in some scenes.

    Virus

    The American crow is very susceptible to the West Nile virus, a disease just recently introduced in North America. American crows usually die within one week of acquiring the disease with only very few surviving exposure. Crows are so affected by the disease that their deaths are now serving as an indicator of the West Nile Virus’ activity in an area.

    Status as an Endangered Species

    Two species of crow have been listed as endangered by the US fish and wildlife services: The ʻAlalā and the Mariana Crow.The American Crow, despite having its population reduced by 45% since 1999 by the West Nile Virus, is considered a Species of Least Concern.

    See also



    References

    • Gill, B. J. (2003): Osteometry and 1: 43-58. (HTML abstract)
    • Worthy, Trevor H. & Holdaway, Richard N. (2002): The lost world of the Moa: Prehistoric Life of New Zealand. Indiana University Press, Bloomington. ISBN 0-253-34034-9.


    External links




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