This species is similar in size (45–47 cm in length) or slightly smaller than the Carrion Crow with black feathers often showing a blue or bluish-purple sheen in bright sunlight. The feathers on the head, neck and shoulders are particularly dense and silky. The legs and feet are generally black and the bill grey-black.
Rooks are distinguished from similar members of the crow family by the bare grey-white skin around the base of the adult's bill in front of the eyes. The feathering around the legs also look shaggier and laxer than the congeneric Carrion Crow. The juvenile is superficially more similar to the Crow because it lacks the bare patch at the base of the bill, but it loses the facial feathers after about six months. A group of rooks is called a parliament.
Distribution and habitatEdit
Though resident in Great Britain, Ireland and much of north and central Europe, vagrant to Iceland and northern Scandinavia. In the north of its range the species has a tendency to move south during autumn though more southern populations are apt to range sporadically also.
Food is predominantly earthworms and insect larvae, which the bird finds by probing the ground with its strong bill. It also eats cultivated cereal grain, smaller amounts of fruit, small mammals, acorns, small birds, their eggs and young and carrion. In urban sites, human food scraps are taken from rubbish dumps and streets, usually in the early hours when it is relatively quiet. It has also been seen along the seashore, feeding on insects, crustaceans and suitable food flotsam.
Nesting in a rookery is always colonial, usually in the very tops of the trees. Branches and twigs are broken off trees (very rarely picked up off the ground), though as many are likely to be stolen from nearby nests as are collected from trees. Eggs are usually 3–5 in number, can appear by the end of February or early March and are incubated for 16–18 days. Both adults feed the young, which are fledged by the 32nd or 33rd day.
In autumn, the young birds of the summer collect into large flocks together with unpaired birds of previous seasons, often in company with Jackdaws. It is during the autumn that spectacular aerial displays can be seen by adult birds that seem to delight in the autumn gales.
The call is usually described as "kaah" – it is similar to that of the Carrion Crow, but usually rather flatter in tone. It is given both in flight and while perched, when the bird fans its tail and bows on each caw. Calls in flight are usually given singly, in contrast to the Carrion Crow's which are in groups of three or four. Solitary birds often "sing" apparently to themselves, uttering strange clicks, wheezes and almost human-like notes.
In captivity, when confronted with problems, rooks have recently been documented as one of multiple species of bird capable of tool use to obtain a goal. They learned that if they push a stone off a ledge into a tube, they will get food. The rooks even quickly discovered they could go get a stone and carry it to the tube if no stone was there already. They also used sticks, wire and even figured out how to bend a wire into a hook to reach an item. Rooks are as clever at making and using simple tools with their beaks as chimpanzees are with their hands.
In an experiment, a rook was placed near a tube of water, with a worm floating on top of the water, and some rocks next to the tube. The water level was too low for the rook to reach the worm. The rook placed rocks into the tube until the water level was high enough for the rook to reach the worm.