The rook's call is a distinctive caw or kaah, variable in pitch and used in different contexts. It is less raucous than that of the carrion crow and is often heard in flight or while perched, where the bird may fan its tail and bow with each call.
Rooks nest colonially in rookeries located at the tops of tall trees. Both sexes contribute to nest-building, which is a cup-shaped structure made of sticks and lined with softer materials. The breeding season begins in spring, with egg-laying occurring by the end of March or early April in Britain, and possibly later in eastern Europe and Russia. The clutch size ranges from three to five eggs, which are incubated primarily by the female.
The birds form flocks in winter, often in the company of other Corvus species or jackdaws. They return to their rookeries, and breeding takes place in spring. They forage on arable land and pasture, probing the ground with their strong bills and feeding largely on grubs and soil-based invertebrates, but they also consume cereals and other plant material. Historically, farmers have accused the birds of damaging their crops and have made efforts to drive them away or kill them. Like other corvids, they are intelligent birds with complex behavioural traits and an ability to solve simple problems.
