It is therefore clear that it is only the outward appearance of the two species that inhibits hybridization. Thus the two species can viably hybridize, and occasionally do so at the contact zone, but the all-black carrion crows on the one side of the contact zone mate almost exclusively with other all-black carrion crows, while the same occurs among the hooded crows on the other side of the contact zone.
Poelstra and coworkers sequenced almost the entire genomes of both species in populations at varying distances from the contact zone to find that the two species were genetically identical, both in their DNA and in its expression (in the form of mRNA), except for the lack of expression of a small portion (<0.28%) of the genome (situated on avian chromosome 18) in the hooded crow, which imparts the lighter plumage colouration on its torso. It is believed that this distribution might have resulted from the glaciation cycles during the Pleistocene, which caused the parent population to split into isolates which subsequently re-expanded their ranges when the climate warmed causing secondary contact. orientalis, are two very closely related species the geographic distributions of both forms of carrion crow across Europe are illustrated in the accompanying diagram. The carrion crow ( Corvus corone) and hooded crow ( Corvus cornix), including the former's slightly larger allied form or race C. Juvenile carrion crows can be identified by their brownish plumage and blue eyes, both of which darken to black and brown as the crow grows older.ĭistribution and genetic relationship to hooded crows Ī map of Europe indicating the distribution of the carrion and hooded crows on either side of a contact zone (white line) separating the two species As well as this, the wings of a carrion crow are proportionally shorter and broader than those of the rook when seen in flight. The beak of the crow is stouter and in consequence looks shorter, and whereas in the adult rook the nostrils are bare, those of the crow are covered at all ages with bristle-like feathers. There is frequent confusion between the carrion crow and the rook, another black corvid found within its range. The carrion crow has a wingspan of 84–100 centimetres (33–39 in) and weighs 400–600 grams (14 oz – 1 lb 5 oz).
It can be distinguished from the common raven by its size of around 48–52 centimetres (19–20 in) in length as compared to an average of 63 centimetres (25 inches) for ravens, and from the hooded crow by its black plumage. The plumage of the carrion crow is black with a green or purple sheen, much greener than the gloss of the rook. brachyrhynchos) in North America.Īdult male carrion crow moulting at the Jardin des Plantes of Paris. Īlong with the hooded crow, the carrion crow occupies a similar ecological niche in Eurasia to the American crow ( C. orientalis) is distinct enough to warrant specific status the two taxa are well separated, and it has been proposed they could have evolved independently in the wetter, maritime regions at the opposite ends of the Eurasian landmass. The hooded crow, formerly regarded as a subspecies, has been split off as a separate species, and there is some discussion whether the eastern carrion crow ( C. The binomial name is derived from the Latin corvus, "raven", and Greek κορώνη korōnē, "crow". The carrion crow was one of the many species originally described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae, and it still bears its original name of Corvus corone.
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