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. [Illustration: ROOK _Corvus frugilegus_ Adult (right). Young (left)] THE SKYLARK Alauda arvensis, Linnæus Of all other birds the Lark is perhaps the one which typifies most thoroughly the freedom of life, and brings to our minds scenes of wide open country, where, bright, free, and unrestrained, he pours forth his song in the boundless expanse of the air.