After the third autumn moult the under parts, head, and neck are much as in the adult birds but more thickly mottled, the back chiefly grey, but the wing coverts, wings, and tail are still very brownish. In their third summer they are practically in adult plumage except for the wings and tail and a remnant of black on the bill. After the fourth autumn moult they are in full adult plumage except that the bill may still show some traces of black and occasionally the tail has some brown flecks, but by the time their fourth summer comes round they are in full adult plumage and breed. Immature birds are seldom seen among colonies of adults during the summer, and it is still somewhat doubtful where they spend the summer; possibly round some islets out at sea where food is plentiful. Length 24 in.; wing 17 in. THE LESSER BLACK-BACKED GULL Larus fuscus, Linnæus Very closely allied to the Herring Gull, this species is tolerably common everywhere, but is rather more local in the breeding season. In England it nests but sparingly and only in the west, but in Scotland it becomes much more abundant, and in some districts commits considerable havoc among the game-birds on the moors. It chooses for its breeding-quarters some grassy slope on the top of the cliffs or on an islet in one of the numerous firths in the west of Scotland. In Ireland it is generally distributed and nests sparingly round the coast. In all its habits this species so closely resembles the Herring Gull that further description is unnecessary. The adult only differs from the preceding species in being black on the mantle and wing coverts, and in the colour of the legs, which are yellow. Length 22 in.; wing 16 in. It is almost impossible to distinguish the young of this species in their first autumn. THE GREATER BLACK-BACKED GULL Larus marinus, Linnæus This species may be found during the winter on almost any part of our shores, but it is by no means so abundant as the Herring Gull.