The rook is around 46 centimetres in length and its black feathers often have a blue or bluish-purple sheen. Its bill is cone shaped and in adults there is bare white skin around its base. The rook has narrower wings than the crow and trouser-like feathers on its upper legs. It makes a croaky "kra-a" sound.
A common sight in fields and urban areas throughout Europe, rooks form colonies that often stay together for decades. They nest in trees between March and May, and females lay between three and five eggs.
Rooks need trees for nesting and open fields for foraging. Some colonies are fairly large, comprising several hundred nests. The nests are built close together, sometimes several dozen in one tree. Rooks are omnivorous, feeding on insects, molluscs, earthworms, small rodents and food waste. In winter, the birds can be seen foraging on rubbish dumps. Belarus is one of the species' wintering locations.