from other members of the crow family. This bare patch gives the false impression that the bill is longer than it is and the head more domed. The feathering around the legs also appears shaggier and laxer than the similarly sized carrion crow, the only other member of its genus with which the rook is likely to be confused. Additionally, when seen in flight, the wings of a rook are proportionally longer and narrower than those of the carrion crow. The average lifespan is six years. The juvenile plumage is black with a slight greenish gloss, except for the hind neck, back and underparts, which are brownish-black. The juvenile is superficially similar to a young crow because it lacks the bare patch at the base of the bill, but it has a thinner beak and loses the facial feathers after about six months. Distribution and habitat Western rooks are resident in the British Isles and much of north and central Europe but vagrant to Iceland and parts of Scandinavia, where they typically live south of 60° latitude. They are found in habitats that common ravens dislike, choosing open agricultural areas with pasture or arable land, as long as there are suitable tall trees for breeding. They generally avoid forests, swamps, marshes, heaths and moorland. They are in general lowland birds, with most rookeries found below , but where suitable feeding habitat exists, they may breed at or even higher. Rooks are often associated with human settlements, nesting near farms, villages and open towns, but not in large, heavily built-up areas. The eastern subspecies in Asia differs in being slightly smaller on average, and having a somewhat more fully feathered face. In the north of its range the species has a tendency to move south during autumn, and more southern populations are apt to range sporadically. The species has been introduced into New Zealand, with several hundred birds being released there from 1862 to 1874. Although their range is very localized, the species is now regarded as an invasive pest and is the subject of active control by many local councils. This has wiped out the larger breeding colonies in New Zealand, and the remaining small groups have become more wary. Behaviour and ecology Rooks are highly gregarious birds and are generally seen in flocks of various sizes. Males and females pair-bond for life and pairs stay together within flocks. In