Corvus




For other uses, see Corvus (disambiguation).









































Crow
Temporal range: 17–0 Ma

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Middle Miocene – Recent


Corvus-brachyrhynchos-001.jpg

American crow (Corvus brachyrhynchos)

Scientific classification edit
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Order:
Passeriformes
Family:
Corvidae
Subfamily:
Corvinae
Genus:
Corvus
Linnaeus, 1758
Species

many, see
Main article: List of Corvus species


Diversity

c. 45 species

Corvus is a widely distributed genus of medium-sized to large birds in the family Corvidae. The genus includes species commonly known as crows, ravens, rooks and jackdaws; there is no consistent distinction between "crows" and "ravens", and these appellations have been assigned to different species chiefly on the basis of their size, crows generally being smaller than ravens.


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 Ethiopia, the 45 or so members of this genus occur on all temperate continents except South America, and several islands. The crow genus makes up a third of the species in the family Corvidae. The members appear to have evolved in Asia from the corvid stock, which had evolved in Australia. The collective name for a group of crows is a "flock" or a "murder".[1] The genus name is Latin for "raven".[2]


Recent research has found some crow species capable of not only tool use, but also tool construction.[3] Crows are now considered to be among the world's most intelligent animals[4] with an encephalization quotient equal to that of many non-human primates.[5]




Contents






  • 1 Description


  • 2 Evolutionary history and systematics


    • 2.1 Species




  • 3 Behavior


    • 3.1 Communal roosting


    • 3.2 Play


    • 3.3 Calls


    • 3.4 Intelligence




  • 4 Diet


  • 5 Reproduction


  • 6 Lifespan and disease


  • 7 Conservation status


  • 8 Problems and methods of control


    • 8.1 Hunting


    • 8.2 Scare tactics


    • 8.3 Trapping


    • 8.4 Other methods




  • 9 As food


  • 10 Human interaction


  • 11 Cultural depictions


    • 11.1 In folklore and mythology


    • 11.2 In popular culture


      • 11.2.1 Literature






  • 12 See also


  • 13 References


  • 14 Further reading


  • 15 External links





Description





Hooded crow (Corvus cornix) in flight





Jungle crow (Corvus macrorhynchos) scavenging on a dead shark at a beach in Kumamoto, Japan


Corvus species are all black or black with little white or grey plumage. They are stout with strong bills and legs. Sexual dimorphism is limited.



Evolutionary history and systematics


Further information: Corvidae



Rook (Corvus frugilegus) on a branch


The members of the genus Corvus are believed to have evolved in central Asia and radiated out into North America, Africa, Europe, and Australia.


The latest evidence[6] regarding the evolution indicates descent within the Australasian family Corvidae. However, the branch that would produce the modern groups such as jays, magpies, and large, predominantly black Corvus species had left Australasia and were concentrated in Asia by the time the Corvus species evolved. Corvus has since re-entered Australia (relatively recently) and produced five species with one recognized subspecies.[citation needed]


The genus was originally described by Linnaeus in his 18th-century work Systema Naturae.[7] The name is derived from the Latin corvus meaning "raven".[8]


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). The genus was originally broader, as the magpie was designated C. pica before being moved later into a genus of its own. At least 42 extant species are now considered to be in this genus, and at least 14 extinct species have been described.


The fossil record of crows is rather dense in Europe, but the relationships among most prehistoric species are not clear. Corvids are found in major cities across the world, and a major increase in the number of crows in urban settings has occurred since the 1900s. Historical records suggest that the population of American crows found in North America has been growing steadily since the introduction of European colonization, and spread east to west with the opening of the frontier. Crows were uncommon in the Pacific Northwest in the 1900s, except in riparian habitats. Populations in the west increased substantially from the late 1800s to mid 1900s. Crows and ravens spread along with agriculture and urbanization into the western part of North America.[9]



Species


Main article: List of Corvus species


Behavior




House crow (Corvus splendens), Bangalore



Communal roosting


Crows gather in large communal roosts numbering between 200 and tens of thousands of individuals during nonbreeding months, particularly in the winter. These gatherings tend to happen near large food sources such as garbage dumps and shopping centers.
[10]



Play


Countless incidents are recorded of corvids at play. Many behaviourists see play as an essential quality in intelligent animals.[11]



Calls









Crows and the other members of the genus make a wide variety of calls or vocalizations.[12] Crows have also been observed to respond to calls of other species; presumably, this behavior is learned because it varies regionally.[13] Crows' vocalizations are complex and poorly understood. Some of the many vocalizations that crows make are a "koww", usually echoed back and forth between birds, a series of "kowws" in discrete units, 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 they vary regionally. In many species, the pattern and number of the numerous vocalizations have been observed to change in response to events in the surroundings (e.g. arrival or departure of crows).




Indian crow in Tamil Nadu



Intelligence


As a group, crows show remarkable examples of intelligence. Natural history books from the 18th century recount an often-repeated, but unproven anecdote of "counting crows" — specifically a crow whose ability to count to five (or four in some versions) is established through a logic trap set by a farmer.[14][15] Crows and ravens often score very highly on intelligence tests. Certain species top the avian IQ scale.[16] Wild hooded crows in Israel have learned to use bread crumbs for bait-fishing.[17] Crows engage in a kind of mid-air jousting, or air-"chicken" to establish pecking order. They have been found to engage in activities such as sports,[18] tool use, the ability to hide and store food across seasons, episodic-like memory, and the ability to use individual experience in predicting the behavior of environmental conspecifics.[19]


One species, the New Caledonian crow, has also been intensively studied recently because of its ability to manufacture and use tools in the day-to-day search for food. On 5 October 2007, researchers from the University of Oxford presented data acquired by mounting tiny video cameras on the tails of New Caledonian crows. They pluck, smooth, and bend twigs and grass stems to procure a variety of foodstuffs.[20][21] Crows in Queensland 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 nontoxic innards; their long beaks ensure that all of the innards can be removed.[22][23]


The jackdaw and the European magpie have been found to have a nidopallium about the same relative size as the functionally equivalent neocortex in chimpanzees and humans, and significantly larger than is found in the gibbon.[24]


Crows have demonstrated the ability to distinguish individual humans by recognizing facial features.[25] Evidence also suggests they are one of the few nonhuman animals, along with insects like bees or ants, capable of displacement (communication about things that are not immediately present, spatially or temporally).[26][27] Ravens have been observed to recruit other ravens to large feeding sites, such as to the carcass of an animal.



Diet





Corvus splendens or house crow resting in shadows on a rooftop with slaughterhouse refuse to eat


Crows are omnivorous, and their diet is very diverse. They will eat almost anything, including other birds, fruits, nuts, mollusks, earthworms, seeds, frogs, eggs, nestlings, mice, and carrion. The origin of placing scarecrows in grain fields resulted from the crow’s incessant damaging and scavenging, although crows assist farmers by eating insects otherwise attracted to their crops.[28]



Reproduction




Nestlings, almost ready to fledge


Crows reach sexual maturity around the age of three years for females and five years for males. Clutch size is approximately three to nine eggs, and the nesting period lasts between 20 and 40 days. Crows often mate for life, and young from previous years often help nesting pairs protect a nest and feed nestlings.
[29]




A crow's nest is made of materials like twigs, electrical wires, metal strips, plastic pieces, and other small items.


Crow nestlings in urban areas face threats such as nest entanglement from anthropogenic nesting materials and stunted growth due to poor nutrition.
[30][31]



Lifespan and disease


Some crows may live to the age of 20, and the oldest known American crow in the wild was almost 30 years old.[32] The oldest documented captive crow died at age 59.[33]


The American crow is highly susceptible to the recently introduced North American strain of West Nile virus.[34] American crows typically die within one week of acquiring the disease and very few survive exposure.



Conservation status




The Hawaiian crow or ʻalala (Corvus hawaiiensis) is nearly extinct; only a few dozen birds survive in captivity. It is listed as "extinct in the wild" by the United States Fish and Wildlife Service.


Two species of crow have been listed as endangered by the U.S. Fish and Wildlife Service: the Hawaiian crow and the Mariana crow.[35]
The American crow, despite having its population reduced by 45% since 1999 by the West Nile virus, is considered a species of least concern.



Problems and methods of control


Intelligence and social structures make most crow species adaptable and opportunistic. Crows frequently cause damage to crops and property,[36] strew trash, and transfer disease. In densely populated areas around the world, corvids are generally regarded as nuisance animals.[37] Crows are protected in the U.S. under the federal Migratory Bird Treaty Act of 1918, but because of their perceived destructive nature, control of the species is allowed in certain areas. Because of their intelligence, control is often difficult or expensive. Methods for control include hunting, chemical immobilization, harassment and scare tactics, and trapping. Before any measure is used to confine, trap, kill, poison, immobilize, or alter the habits of any wild bird species, a person must check local, state, and federal regulations pertaining to such actions.



Hunting


In the United States, hunting is allowed under state and federal regulation. Crow hunting is considered a sport in rural areas of the U.S. because the birds are not considered a tasty traditional game species. Some cultures do treat various corvid species as a food source.[38] Liability and possible danger to persons and property limit the use of hunting or shooting as control methods in urban areas. Crows' wariness and cunning make harvesting crows in sufficient numbers difficult.



Scare tactics


Scare tactics have been the most widely used aversion tactic for crows in areas frequented by humans and domestic animal species. This safe method does not require constant maintenance or manpower to operate or monitor. However, corvids quickly become habituated to most tactics such as blast cannons, predator decoys, and traditional scarecrows. Greater success has been achieved by adding sound and motion to predator decoys to mimic a distressed crow being caught by a predator such as an owl or hawk.[39] Work is currently being done which uses multiple aversion techniques in one area. The theory is that multiple techniques used together will confuse the crows, thereby lessening the probability of habituation to stimuli.



Trapping


Trapping is a rarely used technique in the U.S., but is being used with success in parts of Europe and Australia. The ladder-style trap (e.g., Australian Crow Trap or Modified Australian Crow Trap) seems to be the most effective in crow-trapping techniques. Ladder traps are constructed in such a way that unintentional catch of nontarget species is avoided. If a nontarget species is caught, it can be easily released without harm to the bird. The traps are cost-efficient because they are inexpensive and simple to construct, and require little manpower to monitor. The bait used in the traps can also be specific to corvids. Carrion, grains, unshelled raw peanuts, and shiny objects in the trap are effective baits. When removing crows from a ladder trap, one living crow is left as an extremely effective decoy for other crows. Trapping is considered the most humane method for crow removal because the crows can be relocated without harm or stress. However, most wild birds in general have a knack for returning to their home ranges.[40]



Other methods


Other methods have been used with little or limited success. Lasers have been used successfully to remove large flocks of birds from roost structures in urban areas, but success in keeping crows off roosts has been short-lived.[41] Homeowners can reduce the presence of crows by keeping trash stored in containers, feeding pets indoors, and hanging tin pie-pans or reflective gazing globes around garden areas.



As food


Crows were hunted for survival by Curonians, a Baltic tribe,[42] when common food was exhausted and the landscape changed so that farming was not as productive during the 18th and 19th centuries. Fishermen supplemented their diet by gathering coastal bird eggs and preserving crow meat by salting and smoking it. It became a traditional food for poor folk and is documented in a poem, "The Seasons" by K. Donelaitis. After the nonhunting policy was lifted by the Prussian government in 1721–24 and alternative food supplies increased, the practice was forgotten. The tradition re-emerged after World War I; in marketplaces, butchered crows which were sought after and bought by townsfolk were common. The hunted crows were not the local, but the migrating ones; each year during the spring and autumn, crows migrated via the Curonian Spit between Finland and the rest of Europe. In 1943, the government even issued a hunting quota for such activities. Crows were usually caught by attracting them with smoked fish or grains soaked in spirits and then collecting them with nets. It was a job for the elderly or young who were unable to go to sea to fish, and it was common to catch 150 to 200 birds during a hunting day.



Human interaction


The common raven and carrion crow have been blamed for killing weak lambs and are often seen eating freshly dead corpses probably killed by other means. The Australian raven has been documented chasing, attacking, and seriously injuring lambs.[43] Rooks have been blamed for eating grain in the UK and brown-necked ravens for raiding date crops in desert countries.[44]


Crows have been shown to have the ability to visually recognize individual humans and to transmit information about "bad" humans by squawking.[45] Crows appear to show appreciation to humans by presenting them with gifts.[46][47]



Cultural depictions


See also: Cultural depictions of ravens




Crow on a Branch - Kawanabe Kyosai (1831–1889)



In folklore and mythology





Crow on a branch, Maruyama Ōkyo (1733–1795)




Dhumavati


In Ancient Greece and Rome, several myths about crows and jackdaws included:



  • An ancient Greek and Roman adage, told by Erasmus runs, "The swans will sing when the jackdaws are silent," meaning that educated or wise people will speak after the foolish become quiet.[48]

  • The Roman poet Ovid saw the crow as a harbinger of rain (Amores 2,6, 34).[49]


  • Pliny noted how the Thessalians, Illyrians, and Lemnians cherished jackdaws for destroying grasshoppers' eggs. The Veneti are fabled to have bribed the jackdaws to spare their crops.[50]

  • Ancient Greek authors tell how a jackdaw, being a social creature, may be caught with a dish of oil into which it falls while looking at its own reflection.[50]

  • In Greek legend, princess Arne was bribed with gold by King Minos of Crete and was punished for her avarice by being transformed into an equally avaricious jackdaw, which still seeks shiny things.[51]


In the Bible account at 1 Kings 17:6, ravens are credited with providing Elijah food.





The Twa Corbies by Arthur Rackham


In Australian Aboriginal mythology, Crow is a trickster, culture hero, and ancestral being. Legends relating to Crow have been observed in various Aboriginal language groups and cultures across Australia; these commonly include stories relating to Crow's role in the theft of fire, the origin of death, and the killing of Eagle's son.


Crows are mentioned often in Buddhism, especially Tibetan disciplines. The Dharmapala (protector of the Dharma) Mahakala is represented by a crow in one of his physical/earthly forms.[citation needed]


In the Chaldean myth, the Epic of Gilgamesh, Utnapishtim releases a dove and raven to find land; however, the dove merely circles and returns. Only then does Utnapishtim send forth the raven, which does not return, and Utnapishtim concludes the raven has found land.[52]


In Chinese mythology, the world originally had 10 suns either spiritually embodied as 10 crows and/or carried by 10 crows; when all 10 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.[53][54]


In Denmark, the night raven is considered an exorcised spirit. A hole in its left wing denotes where the stake used to exorcise it was driven into the earth. He who looks through the hole will become a night raven himself.[55]


In Hinduism, crows are thought of as carriers of information that give omens to people regarding their situations. For example, when a crow crows in front of a person's house, the resident is expected to have special visitors that day. Also, in Hindu literature, crows have great memories which they use to give information.[citation needed] Symbolism is associated with the crow in the Hindu faith. On a positive note, crows are often associated with worship of ancestors because they are believed to be embodying the souls of the recently deceased. However, many other associations with crows are seen in Hinduism. Crows are believed to be connected with both the gods and goddesses, particularly the controversial ones such as Sani, the god of the planet Saturn, who uses a crow as his vehicle. In Hindu astrology, it is said that one who has the effect of Sani in their horoscope are angered easily, and may be unable to take control of their futures, but are extremely intelligent at the same time. Thus the presence of a crow, the vehicle of Sani is believed to have similar effects on the homes it lays its eyes on. Whether these effects are positive or negative is a source of debate in Hinduism.[56] Crows are also considered ancestors in Hinduism and during Śrāddha, the practice of offering food or pinda to crows is still in vogue.[57] Crows are associated with Dhumavati the form of mother goddess that invokes quarrel and fear.[58] Crows are also fed during the fifteen day period of Pitru Paksha, which occurs in the Autumn season, as an offering and sacrifice to the ancestors. During the time of Pitra Paksha, it is believed that the ancestors descend on earth from pitra-loka, and are able to eat food offered to them by the means of a crow. This can also occur during the time of Kumbha, many Hindus prepare entire vegetarian meals that are eaten solely by the crows and other birds.


In Irish mythology, crows are associated with Morrigan, the goddess of war and death.[59]


In Islam, according to a narration in the Hadith, the crow is one of the five animals for which no blame is placed on the one who kills them.[60] The Surat Al-Ma'ida describes the story of how the crow teaches son of Adam to cover dead body of his brother "Then Allah sent a crow digging up the earth so that he might show him how he should cover the dead body of his brother. He said: Woe me! do I lack the strength that I should be like this crow and cover the dead body of my brother? So he became of those who regret.".[61]


In Japanese mythology, a three-legged crow called Yatagarasu (八咫烏, "eight-hand-crow")[62] is depicted.[63]


In Korean mythology, a three-legged crow is known as Samjokgo (hangul: 삼족오; hanja: 三足烏).[citation needed]


In Norse mythology, Huginn and Muninn are a pair of common ravens that range the entire world, Midgard, bringing the god Odin information.


In Sweden, ravens are held to be the ghosts of murdered men.[64]


In Welsh mythology, the god Brân the Blessed – whose name means "crow" or "raven" — is associated with corvids and death; tradition holds that Bran's severed head is buried under the Tower of London, facing France — a possible genesis for the practice of keeping ravens in the Tower, said to protect the fortunes of Britain. In Cornish folklore, crows — magpies particularly — are associated with death and the "other world", and must be greeted respectfully. The origin of "counting crows" as augury is British; however, the British version rather is to "count magpies" — their black and white pied colouring alluding to the realms of the living and dead.


In some Native American mythologies, especially those in the Pacific Northwest, the raven is seen as both the Creator of the World and, separately, a trickster god.


In medieval times, crows were thought to live abnormally long lives. They were also thought to be monogamous throughout their long lives. They were thought to predict the future, to predict rain and reveal ambushes. Crows were also thought to lead flocks of storks while they crossed the sea to Asia.[65]



In popular culture



Literature



  • In Aesop's Fables, the jackdaw embodies stupidity in one tale (by starving while waiting for figs on a fig tree to ripen), vanity in another (the jackdaw sought to become king of the birds with borrowed feathers, but was shamed when they fell off),[66] and cunning in yet another (the crow comes up to a pitcher and knows that his beak is too short to reach the water, and if he tips it over, all the water will fall out, so the crow places pebbles in the pitcher so the water rises and he can reach it to relieve his thirst).[67]

  • The British Poet Laureate Ted Hughes combined some of the Amerindian and Celtic myths mentioned above in writing the 1970 poetry collection Crow: From the Life and Songs of the Crow (1970).

  • In Ovid's Metamorphoses, in Greek mythology, the god Apollo became enraged when the crow exposed his lover Coronis' tryst with a mortal, his ire transmuting the crow's feathers from white to black.[68]

  • In the Story of Bhusunda, a chapter of the Yoga Vasistha, a very old sage in the form of a crow, Bhusunda, recalls a succession of epochs in the earth's history, as described in Hindu cosmology. He survived several destructions, living on a wish-fulfilling tree on Mount Meru.[69]



See also



  • Corvus (heraldry)

  • Eating crow


  • Ischys for the Greek myth of why the crow's feathers are black

  • Scarecrows



References





  1. ^ "Murder of Crows, etc". Word-detective.com. Retrieved 12 November 2011..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}


  2. ^ Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. p. 119. ISBN 978-1-4081-2501-4.


  3. ^ Winkler, Robert (8 August 2002). "Crow Makes Wire Hook to Get Food". National Geographic. Retrieved 6 February 2011.


  4. ^ "A Murder of Crows". Nature. PBS video. 24 October 2010. Retrieved 6 February 2011. New research indicates that crows are among the brightest animals in the world.


  5. ^ "Crows as Clever as Great Apes, Study Says". National Geographic News. NG Society. 9 December 2004. Retrieved 24 June 2015. Emery and Clayton write, "These studies have found that some corvids are not only superior in intelligence to birds of other avian species (perhaps with the exception of some parrots), but also rival many nonhuman primates."


  6. ^ Barker, F. K.; Cibois, A.; Schikler, P.; Feinstein, J.; Cracraft, J. (2004). "Phylogeny and diversification of the largest avian radiation". Proceedings of the National Academy of Sciences. 101 (30): 11040–5. doi:10.1073/pnas.0401892101. PMC 503738. PMID 15263073.


  7. ^ Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata (in Latin). Holmiae. (Laurentii Salvii). p. 824. Archived from the original on 19 March 2015.


  8. ^ Simpson, D.P. (1979). Cassell's Latin Dictionary (5 ed.). London: Cassell Ltd. p. 883. ISBN 978-0-304-52257-6.


  9. ^ Marzluff, J., Bowman, R. and Donnelly, R. (2001). Avian ecology and conservation in an urbanizing world. Boston: Kluwer Academic Publishers.


  10. ^ Caccamise, D., Reed, L. and Stouffer, P. (1997). Roosting Behavior and Group Territoriality in American Crows. The Auk, 114(4), 628-637.


  11. ^ Bekoff, Mark & Byers, John (1998). Animal Play: Evolutionary, Comparative and Ecological Perspectives.


  12. ^ Chamberlain, Dwight R; Cornwell, George W (1971). "Selected Vocalizations of the Common Crow". The Auk. 88 (3): 613–634. JSTOR 4083753.


  13. ^ Shanbhag, Anirudh P.; Ghosh, Ishita; Umakanth, B. DOI: 10.5829/idosi.gjer.2012.6.1.6184 Interspecific Behavioral Studies of House Crows (Corvus splendens protegatus) and Jungle Crows (Corvus macrorhynchos culminatus) on Mutual Foraging Sites. CiteSeerX 10.1.1.414.3107.


  14. ^ Dehaene, Stanislas (2011). The Number Sense: How the Mind Creates Mathematics, Revised and Updated Edition. Oxford University Press. pp. 289–. ISBN 978-0-19-975387-1.


  15. ^ Park, Keeok. Numbers Are Us. Keeok Park. pp. 19–. ISBN 978-0-9843446-3-5.


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  20. ^ Schmid, Randolph E. (5 October 2007) "Crows Bend Twigs Into Tools" at the Wayback Machine (archived 31 March 2012), Associated Press via Discovery Channel


  21. ^ See also the video "Crow bars", from the BBC's The Life of Birds


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  23. ^ "Cane Toad (Bufo marinus)". Ozanimals.com. Retrieved 12 November 2011.


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  27. ^ Heinrich, B.; Marzluff, J. M. (1991). "Do common ravens yell because they want to attract others?". Behavioral Ecology and Sociobiology. 28. doi:10.1007/BF00172134.


  28. ^ Crow Facts. crowbusters.com


  29. ^ Allaboutbirds.org, (2014). American Crow. [online] Available at: http://www.allaboutbirds.org/guide/american_crow/lifehistory


  30. ^ Andrea K Townsend and Christopher M Barker (2014). Plastic and the Nest Entanglement of Urban and Agricultural Crows
    Heiss, R., Clark, A. and McGowan, K. (2009).


  31. ^ Growth and nutritional state of American crow nestlings vary between urban and rural habitats. Ecological Applications, 19(4), 829-839.


  32. ^ McGowan, K.J. "Frequently Asked Questions About Crows", Cornell Lab of Ornithology


  33. ^ Crow Believed to Be Oldest in World Dies. Associated Press via Washington Post (7 July 2006)


  34. ^ "Why West Nile virus kills so many crows", Penn State Center for Infectious Disease Dynamics


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Further reading


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  • Burton, Maurice; Burton, Robert (2002). "Crow". The international wildlife encyclopedia, Volume 10. Marshall Cavendish. ISBN 978-0-7614-7266-7.


  • Gill, B. J. (2003). "Osteometry and Systematics of the Extinct New Zealand Ravens (Aves: Corvidae: Corvus)". Journal of Systematic Palaeontology. 1: 43–58. doi:10.1017/S1477201903001019. Retrieved 14 March 2008.


  • Goodwin, D. (1983). Crows of the World. Queensland University Press. ISBN 978-0-7022-1015-0.


  • Heinrich, Bernd (1991). Ravens in Winter. Vintage Press. ISBN 978-0-679-73236-5.


  • Heinrich, Bernd (1999). Mind of the Raven: Investigations and Adventures with Wolf-Birds. Cliff Street Books. ISBN 978-0-06-093063-9.


  • Kilham, Lawrence (1991). The American Crow and the Common Raven. Texas A&M University Press. ISBN 978-0-89096-466-8.


  • Madge, Steve; Burn, Hillary (1994). Crows and jays: a guide to the crows, jays, and magpies of the world. Houghton Mifflin. ISBN 978-0-395-67171-9.


  • Westerfield, Michael (2011). The Language of Crows: The crows.net Book of the American Crow. Ashford Press. ISBN 978-0-937992-00-5.


  • Worthy, Trevor H.; Holdaway, Richard N. (2002). The Lost World of the Moa: Prehistoric Life of New Zealand. Indiana University Press. ISBN 978-0-253-34034-4.




External links












  • Frequently Asked Questions About Crows - Cornell Lab of Ornithology


  • Crows (Corvidae) - Internet Bird Collection

  • Crows.net: The Language and Culture of Crows


  • Tool making and use by Crows - Behavioural Ecology Research Group, Oxford University


  • "A Murder of Crows" - PBS documentary (2010)











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