This species breeds in the Outer Hebrides, the Orkneys, and the Shetlands; it is also said to be a regular breeder in Sutherlandshire. It is a much more numerous species than the great skua, being a regular visitor to the coasts of Scotland in the autumn and spring migrations. In its preying habit it resembles the bonxie, but, unlike that species, is gregarious. It breeds on moors, often at a considerable distance from the sea, and its nests are widely scattered on the breeding-ground. A slight hollow in the ground, with a little dry grass for lining, serves as a receptacle for the eggs. Two eggs are laid, and in some cases only one. These vary greatly in shape, some being nearly round, others long and pointed. In ground-colour they vary from russet-brown to pale olive, and are evenly and sparingly spotted with dark brown. A curious fact about this species is that there are two forms, one light in colour, the other dark, and that these habitually interbreed; but the young, instead of being intermediate, are, according to Seebohm, light or dark, like one of the parents. * * * * * The pomatorhine skua (_S. pomatorhinus_) is an autumn and spring visitor on migration to the seas in the vicinity of the British coasts. In some seasons it occurs in large numbers, but is not very regular in its appearance. Buffon’s skua (_S. parasiticus_) is a rare and irregular visitor on migration to the British coasts. It breeds in the arctic regions, and is circumpolar. Stormy Petrel. Procellaria pelagica. Upper parts black, except the tail-coverts, which are white at their bases; edges of the wing-coverts slightly edged with white; under parts sooty black; bill and feet black. Length, six inches. * * * * * The names of stormy petrel and Mother Carey’s chicken are as familiar to everyone as that of rook, or partridge, or hedge-sparrow; but the little bird they belong to is known by sight to comparatively few persons. It is pre-eminently an oceanic species, that comes to land only to breed; its breeding-places are on remote and lonely islands not easy of access; and, when breeding, the bird is nocturnal in habits, and it would be possible for anyone to spend many days in the very midst of a colony of petrels and not see them, or suspect that they were there. [Illustration: FIG. 112.--STORMY PETREL. ⅓ natural size.]