There is no more delightful sound in early spring than the “caw” of the Rooks at their “rookeries,” as their breeding places are called. Year after year they return regularly to the same clump of trees, on the tops of which they build a fairly substantial nest of sticks, with an inner foundation of mud which is in turn warmly lined with roots, straw, and fine grass. The sites chosen for their homes are more frequently than not near human habitations or on clumps of trees near a highway, and exceptionally, they may choose pollards or low bushes, but as a rule the nests are never less than twenty feet from the ground. The eggs are bluish, with olive brown spots and blotches resembling those of the Carrion Crow, but smaller and more variable.

The young leave the nest just before they can fly, and may then be seen sitting on the topmost branches of the trees as they sway in the wind. This is the time when they are shot for rook-pies, and also under the impression that if they are not thinned out the colony will be deserted. For this belief we are not aware that any proof exists, but curiously enough colonies left to themselves tend to diminish. These birds are rather capricious and will occasionally, even in the nesting season, desert the colony; the presence in the neighbourhood of a pair of Carrion Crows is sometimes the cause, but more often than not the reason is not apparent. As soon as the young can fly, towards the middle or end of May, the rookery is deserted: old and young keep together and wander about the fields and arable land, digging deeply with their powerful bills in search of larvÆ and grubs, and destroying countless numbers of wire worms, that renowned pest to agriculture. In this country it does not migrate to any extent; certain plantations are used as regular roosting-places, and as evening draws on in the winter months, long strings of these birds may be seen slowly flying in their heavy characteristic manner to their nightly shelter. Although the flight appears heavy and laboured, they in reality travel at no mean pace, and in their daily search for food often cover great distances. As in the case of Jackdaws and Jays, there is a large immigration yearly on our east coast during October and November, for in Scandinavia and the northern portions of its breeding range it is a regular migrant. Throughout the whole of our islands it is a common bird, but is rather more local in Scotland, and it is only of recent years that it has regularly bred in the extreme north. From continual digging in the ground the feather follicles round the base of the bill become destroyed, leaving a whitish patch of bare skin which is an unfailing characteristic of the adult birds. In young individuals, however, the feathers extend to the base of the bill and do not appear to be permanently lost till during the second autumn moult. The sexes are alike; their colour is a uniform deep and glossy purplish blue. The young resemble their parents, but lack the gloss to their feathers. Length 19 in.; wing 12·65 in.