Carrion crows () are found throughout Europe and much of Asia. In Europe, they range from the northern coast of Sweden extending to the southern coast of Spain. Their western boundary is the Atlantic Ocean. In Asia, the southern boundary runs through Iraq and Iran, most of Afghanistan, and the northern region of China. They also inhabit all of Japan. The northern border of their range cuts through the center of Russia, extending to the eastern coast of Russia.
Their breeding range extends further northwards in Russia, reaching just north of the Arctic Circle, to around 70 degrees north. There is also a small African population, which has extended the range South through the Middle East to live along the Nile River in Egypt. (BirdLife International, 2014; Peterson, et al., 1954)
Carrion crows live in a variety of habitats. Historically, they lived in marshlands, lightly cultivated areas with sparse tree cover, and on coasts. More recently, they have adapted to suburban and urban areas to an incredible degree. They use parks and buildings for nesting, and forage for food in landfills and dumpsters. Individuals in cities have very similar foraging success to those in non-urban environments. The only major detriment observed is a decrease in nutritional health. They are not limited by elevation, existing from sea level up into mountainous areas. Carrion crows tend to nest in trees or on cliffs. (Baglione, et al., 2002; Peterson, et al., 1954)
is a uniformly black bird, averaging 47 cm in length. It weighs between 300 - 450 grams as an adult. In certain light, its feathers appear glossy. The male and female look alike.
Crows' feet are anisodactyl, with three forward-facing toes, and one back-facing toe. The wingspan of an adult carrion crow is between 84 and 100 cm. It looks very similar to an immature rook, Corvus frugilegus, but can be distinguished by the carrion crow's larger beak. It is nearly identical to a raven, Corvus corax, except for the carrion crow's much smaller size and lighter bill. (Peterson, et al., 1954; Richner, 1989)
Carrion crows form monogamous pairs, which stay together for life. They breed in early spring, from March to April. In most cases, these pairs defend the same territory they live in year-round. Some populations may migrate to a mating site.
In a shared breeding ground in Spain, carrion crows have been known to mate with hooded crows, Corvus cornix. These matings produce viable hybrids which show similar reproductive success to non-hybrid individuals.
Each nest consists of just one mated pair. However, around 3% of individuals engage in cooperative mating. In particular, a population in northern Spain has been shown to have cooperative mating in a majority of nests. In most cases, the helper birds were related to the mating pair. In a few cases, these breeding groups reached sizes of fifteen birds, sometimes with nestlings from multiple pairs. Due to the rarity of this, studies have only recently began to examine the mechanics of the breeding groups. (Baglione, et al., 2002; Perrins, 2009; Randler, 2007a)
Each spring, a pair of carrion crows lays one clutch of four to five eggs. These eggs take seventeen to twenty days to hatch. The nestlings mature for an additional twenty-eight to thirty days in the nest before they fledge. Both the male and female of the species take an average of three years to begin reproduction. In some cases, young carrion crows stay with their parents for up to two years to learn foraging behaviors, or to help raise future offspring of the parents. (Baglione, et al., 2002; Perrins, 2009; Randler, 2007b)
Carrion crow mated pairs defend their nesting territory throughout the year. Both individuals are involved in the nest-making process. Only the female incubates the eggs, while the male continues to defend the territory and provide provisions to the female as needed. After hatching, both parents defend and feed the nestlings. There have been documented instances of parents and offspring feeding together after the offspring have fledged. In a small number of cases, the offspring help the parents with future years of reproduction. (Baglione, et al., 2002; Perrins, 2009; Randler, 2007b)
About half of all carrion crows do not live past their first year. In the wild, those that do live beyond 1 year tend to live until around ten years of age. In captivity, they have been known to live as long as 29 years, with the oldest birds dying of mental deterioration, indicating this is a true maximum to their age. (Perrins, 2009)
Carrion crows live in flocks known as murders until they mate. Murders often consist of members of a few separate families. These groups often roam a large area, using their numbers to compete for resources. Once they find a mate, they leave the flock and claim territory. After establishing their territory, mated pairs defend this territory year-round in most populations. In populations living in colder territories, the pair may migrate during the winter months, moving south to a warmer climate.
has shown extremely complicated patterns of behavior. Individuals of the species have been shown using tools, such as sticks to reach food items in a laboratory setting. In the wild, they have been observed using cars to open nuts too hard for them to break with their beak. There is also evidence that carrion crows can become familiar with individuals of other species. Cibulski et al. (2014) found that captive carrion crows performed better on tests when they had prior experience with the individual administering the test. This has also been observed in the wild with individual carrion crows interacting with humans who live near their territory.
Carrion crows are known to either defend a territory in pairs or to roam an area in flocks of five to twenty birds known as murders. In general, only breeding pairs defend a territory, while non-breeding crows travel looking for food and other resources. (Baglione, et al., 2002; Cibulski, et al., 2013; Hoffmann, et al., 2011; Moll and Nieder, 2014; Wascher, et al., 2014)
Mated pairs of carrion crows defend areas of 200 - 500 square meters (average 475 square meters). Murders of younger birds move across a much wider area, which has not been quantified sufficiently in the literature. (Baglione, et al., 2002; Bossema and Benus, 1985; Perrins, 2009)
Carrion crows have a highly sophisticated ability to track objects visually. As seen in a study by Hoffmann et al. (2011), they are able to track objects even when the object in question is out of sight. They were able to successfully learn to follow out-of-sight items during variations of the classic shell game, find hidden objects based on visual cues, as well as locate objects deceptively hidden. In all cases, carrion crows were able to discover the object within the perimeters of the test after minimal learning time.
Additionally, carrion crows have shown response to olfactory cues. When exposed to familiar scents, crows were more likely to respond than they did to unfamiliar smells. Evidence shows carrion crows react to odor clues involved with foraging, predator avoidance, and recognition of other birds, including partners and kin.
Finally, carrion crows have shown the ability to mimic sounds, including human speech. However, their typical wild call is characteristic of other crow species. It sounds like "crow!" with a harsh, sometime guttural, tone to it. (Hoffmann, et al., 2011; Wascher, et al., 2014)
Carrion crows are omnivores, consuming carrion, living invertebrates, and the seeds and nuts of plants. They have also been known to steal crops from humans, especially corn, Zea mays. There have been many reported instances, some with documented evidence, of engaging in extremely complicated foraging behaviors. They have been seen stealing fish from baited lines by pulling the line in with their beak and feet, as well as using cars to crack nuts too strong for their beak.
Carrion crows are often seen caching food. When facing competition from other birds, they often harvest much more food than is needed at one time and hide it. Studies have shown they can remember hundreds or even thousands of locations, as well as remember individual items hidden there. It has been observed that they return to and eat perishable food items before items that will keep for longer times. (Perrins, 2009)
No research has been conducted into specific predators of carrion crows. However, in other members of the family Corvidae, hawks, eagles, owls and raccoons are known predators. (Perrins, 2009; Peterson, et al., 1954)has been known to attack birds of prey in large groups, a behavior known as mobbing. Often, this behavior occurs when a bird of prey enters the vicinity of a murder, even if it makes no aggressive move towards the group. This almost always results in the retreat of the predator.
Carrion crows can significantly affect local populations of birds by preying on their eggs (Fletcher et al. 2013). This indicates they likely perform a role in population control on their ecosystem by reducing brood sizes in other birds. In addition, carrion crows consume carrion, but the significance of their contribution in this respect is unknown. The great spotted cuckoo, Clamator glandariou, is a brood parasite known to lay eggs in carrion crow nests.
Parasites of this crow include roundworms Aprocta matronensis, Acuaria anthuris, Acuaria depressa and Roberdollfusa paradoxa. (Anderson, 2000; Fletcher, et al., 2013; Manfredi, et al., 1992; Soler, 1990)
There is some anecdotal evidence that carrion crows help to control pest species by feeding on insect larva and small bird eggs, but no research has been conducted. (Perrins, 2009)
There are reports of carrion crows killing young livestock, but research suggests this is vastly overestimated by the public. It is unlikely that this occurs often enough to have any significant effect on the economy. (Lack, 2011)
Phillip James (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
living in landscapes dominated by human agriculture.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
flesh of dead animals.
uses smells or other chemicals to communicate
helpers provide assistance in raising young that are not their own
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats fruit
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
An animal that eats mainly insects or spiders.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
imitates a communication signal or appearance of another kind of organism
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
an animal that mainly eats all kinds of things, including plants and animals
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
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