Rooks are omnivorous; they eat a very broad range of food, including earthworms and other invertebrates (2), seeds and waste root crops in winter (4). They feed on the ground, often inserting the beak into the soil, and may bury food for consumption at a later time (5). This bird is very sociable, and nests communally in groups of trees known as 'rookeries' (5). Communal roosts form in winter, consisting of birds from a number of breeding rookeries (4). These roosts can be huge; one in northwest Scotland contained 65,000 rooks (4). By February, the rooks return to their own rookery in order to start breeding (4); pairs defend a small area around their nests. During courtship, the male struts around, bowing, posturing and cawing; he may then empty the contents of his food pouch into the female's mouth before mating takes place (5). The nest is constructed of twigs, and 3-5 blue or grey-green eggs are laid towards the end of March. These are incubated by the female for up to 18 days; whilst the female incubates the eggs and broods the chicks she is fed by the male (5). After 40 days, the chicks are fully grown, but they remain dependent on their parents for food until they reach 60 days of age, and only become truly independent after around 5 months (5). Like many members of the crow family, the rook figures heavily in folklore. The sudden desertion of a rookery was said to be a bad omen for the landowner. Rooks are believed to indicate rain by certain behaviour (6), and are also believed to be able to smell approaching death (5).