crow city | crow family | carrion & hooded crow | rook | jackdaw | magpie | jay | chough | raven
The rook is only likely to be confused with the carrion crow, yet the rook’s bill is more slender and the adult rook has a bare pale grey face. The rook’s wing beats are also slightly faster through the sky. The rook is black with blue and purple iridescence, becoming greener on the wings and tail. The beak, legs and feet are black and the eye is a dark brown.
Rooks are very colonial birds and therefore have but a small amount of tree around their nest to call their own. The male is most aggressive during the nest building period, most probably due to their testes producing more male hormone at this time. Once they have mated the amount of male hormone produced will begin to drop away, a refractory period lasting from June to August. Some rooks mate for several years, possibly life if they both survive, often using the same nest year after year. Once the young have left the nest they may wander long distances from their natal rookery, possibly returning once they have paired. The male will find a high and solitary spot during the autumn and winter and sing. If a female comes and accepts food from him the pair has been formed.
Rookeries are rarely found in woodland, the birds preferring a measure of open country. Most nests are in deciduous trees, although evergreens are favoured where protection from frequent and virulent gales is a concern. Electricity pylons will sometimes be chosen. The female is able to build the whole nest herself but is normally helped by the male with the outer layer of twigs. She will fetch and shape the majority of the lining, with leaves, grass and earth followed by paper, fur and feathers.
Outside of the breeding season, and especially where there are large numbers of wintering migrators, the communal roost is very important in making the most of available food supplies, as birds who have fed poorly can try their luck the following day with ones who have had more success. It also offers protection from predators and from the cold. Both the roost and the rookery are used as meeting places throughout the day, where birds will congregate before leaving on another feeding trip. Birds from different rookeries will feed together, there being no feeding territory associated with individual rookeries.
Rooks are the keenest probers of the crows and consequently earthworms and leatherjackets are very important to their diet. They also enjoy pecking at scuttling or flying insects. When the flock is feeding, the birds will take it in turns to stand sentry, allowing the other birds to feed far more efficiently. Grain is popular, preferred before it has started to sprout. Their habits are closely tied with agriculture and the changing seasons since they are primarily rural birds. Most studies on rooks has been to establish whether they are a danger or a help to arable farming. This is always a difficult question to answer, since there are so many variable factors, the pendulum swinging from one moment to another, but there can be no doubt that they are extremely valuable in their control of weevils and larvae. Cannibalism is much rarer in rooks than in the carrion crow.
Albinism occurs in rooks as in other crows, affecting even their beaks and legs. Shooting does not control the rook population since other rooks will join the flock if there are sufficient food sources, and all crows will continue to feed even where their dead fellows have been strung up.
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