Corvo comune

Identificazione

The plumage of the carrion crow is black with a green or purple sheen, much greener than the gloss of the rook (Corvus frugilegus). The bill, legs and feet are also black. 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 carrion crow has a wingspan of 84–100 centimetres (33–39 in) and weighs 400–600 grams (14 oz – 1 lb 5 oz).<p>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.

Tassonomia

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. The binomial name is derived from the Latin corvus, "raven", and Greek κορώνη korōnē, "crow".<p>The hooded crow (Corvus cornix), formerly regarded as a subspecies, has been split off as a separate species, and there is some discussion whether the eastern carrion crow (C. 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.<p>Along with the hooded crow, the carrion crow occupies a similar ecological niche in Eurasia to the American crow (Corvus brachyrhynchos) in North America. The two species look very similar to one another, but can be differentiated by size, as the carrion crow is larger and of a stockier build compared to the American crow.

Nome scientifico

Corvus corone

Autorità

Linnaeus, 1758

Ordine

Passeriformi

Famiglia

Corvidi

Genere

Corvus

Areale e habitat

Migrazione

Complete migrants

Comportamento

The rook is generally gregarious and the crow largely solitary, but rooks occasionally nest in isolated trees, and crows may feed with rooks; moreover, crows are often sociable in winter roosts. The most distinctive feature is the voice. The rook has a high-pitched kaaa, but the crow's guttural, slightly vibrant, deeper croaked kraa is distinct from any note of the rook.<p>The carrion crow is noisy, perching on a vantage point such as a building or the top of a tree and calling three or four times in quick succession, with a slight pause between each series of croaks. During each series of calls, a crow may perform an accompanying gesture, raising its shoulders and bowing its head and neck downwards with each caw. The wing-beats are slower, more deliberate than those of the rook.<p>Carrion crows can become tame near humans, and can often be found near areas of human activity or habitation including cities, moors, woodland, sea cliffs and farmland where they compete with other social birds such as gulls, other corvids, and ducks for food in parks and gardens.<p>Like other species of corvid, carrion crows will actively harass predators and competitors that enter their territory or threaten them or their offspring, and will engage in group mobbing behaviour as a method to defend themselves.<p>Like all corvids, carrion crows are very intelligent. For example, they can discriminate between numerosities up to 30, flexibly switch between rules, and recognise human and crow faces. Given the difference in brain architecture in crows compared to primates, these abilities suggest that their intelligence is realised as a product of convergent evolution.<p>Though an eater of carrion of all kinds, the carrion crow will eat insects, earthworms, other invertebrates, grain, fruits, seeds, nuts, small mammals, amphibians, fish, scraps and will also steal eggs. Crows are scavengers by nature, which is why they tend to frequent sites inhabited by humans in order to feed on their household waste. Crows will also harass birds of prey or even foxes for their kills. Crows actively hunt and occasionally co-operate with other crows to make kills, and are sometimes seen catching ducklings for food. Due to their gregarious lifestyle and defensive abilities, carrion crows have few natural predators. However, powerful raptors such as the Eurasian goshawk, peregrine falcon, Eurasian eagle-owl and golden eagle will readily hunt them, and crows can become an important prey item locally.<p>The bulky stick nest is usually placed in a tall tree, but cliff ledges, old buildings and pylons may be used as well. Nests are also occasionally placed on or near the ground. The nest resembles that of the common raven, but is less bulky. The 3 to 4 brown-speckled blue or greenish eggs are incubated for 18–20 days by the female alone, who is fed by the male. The young fledge after 29–30 days.<p>It is not uncommon for an offspring from the previous years to stay around and help rear the new hatchlings. Instead of seeking out a mate, it looks for food and assists the parents in feeding the young.

Conservazione

Tendenza della popolazione

rising