In adult plumage the Gulls are not remarkable for any great diversity of colour. French gray predominates upon the upper parts; the under parts are white, often suffused with a delicate rosy tint; the primaries are usually dark gray, brown, or black, in many species spotted and tipped with white. Some species assume (by a change of colour and not by a moult) a sooty-brown or black head or hood during the breeding season; Ross’s Gull dons a black narrow collar at that period. The wings are ample, long, and pointed; the tail is even, except in Ross’s Gull in which it is wedge-shaped, and in Sabine’s Gull in which it is forked. The legs are comparatively short, and the feet are webbed. Gulls moult twice in the year. When first hatched young Gulls are covered with down. Young, in first plumage of the Black-headed group of Gulls, have the feathers of the mantle, the scapulars, and the innermost secondaries, brown with pale margins; the crown, nape, and ear-coverts brown; and the tail with a broad sub-terminal band of the same colour. The second plumage—assumed as soon as the foregoing is completed—retains brown marks of immaturity on the scapulars and innermost secondaries; the wing-coverts are streaked with brown, and the tail still retains its brown sub-terminal band. This plumage is carried until the following spring, when the brown hood—assumed for the first time—is mottled with white; the tail-band is more or less broken; whilst the scapulars and innermost secondaries assume the colour peculiar to the adult. For several years the white markings on the primaries gradually increase in extent until the bird arrives at perfect maturity. The larger Gulls—of which the Herring Gull may be taken as a typical species—mature much more slowly, the perfectly adult plumage not being assumed until the bird is four years old. The plumage succeeding the downy stage is brown on the upper parts, each feather with a pale margin, and white on the under parts streaked with brown. After each succeeding moult in spring and autumn, the traces of immaturity grow less, the wing-coverts and tail retaining them longest. The white spots on the primaries are the latest signs of complete maturity. The colour of the feet, bill, iris, and irides, slowly changes until that characteristic of the adult is assumed.