The Carrion Crow (Corvus corone) can be distinguished from the Common Raven by its size (48″“52 cm in length) and from the Hooded Crow by its black plumage. There is frequent confusion between it and the Rook. The beak is stouter and in consequence looks shorter, and whereas in the adult Rook the nostrils are bare, those of the crow are covered with bristle-like feathers, in both adults and juveniles.
This species breeds in western and central Europe, with an allied race (C. c. orientalis_ and is 50-56 cm in length and occurs in eastern Asia. The separation of these two populations is now believed to have taken place during the last ice age, with the closely allied Hooded Crow (now given species status) filling the gap between. Fertile hybrids occur along the boundary between these two forms indicating their close genetic relationship.
The plumage of Carrion Crow is black and has a green or purple sheen, but the gloss is much greener than that of the Rook. The bill, legs and feet are also black.
The Rook is generally gregarious, whereas the crow is 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 its voice. The rook says caw, but the Crow calls pawk pawk. The guttural, slightly vibrant croak is distinct from any note of the rook.
This bird is talkative and loves to perch on the top of a tree, calling three or four times in quick succession, with a slight pause between each series of croaks. The wing-beats are slower, more deliberate than those of the Rook.
Even though the Crow is a carrion eater, it will kill and eat any small animal it can catch, and is an chronic egg-robber. Crows are by nature scavengers, which is why they tend to frequent sites inhabited by humans in order to feed on their household leavings.
The Crow nests on cliff ledges but in inland locations it is arboreal; the nest is similar to that of the raven, but somewhat less bulky. The eggs, four or five in number, are seldom laid before April; they are blotched and spotted with brown on a blue or green background and vary considerably. Young birds are fledged and ready to leave the nest within only six or so weeks of hatching.
It is not uncommon for an offspring from the previous years to stay around and help rear the new hatchlings. It will not, itself, take a mate but will instead search for food and assist the parents with feeding the young.