As a rule they chase Gulls and Terns, compelling them by so doing to disgorge their last meal; this the Skua then devours, leaving the Gull in peace to hunt for more. They are not, however, always content with this second-hand dinner, but sometimes kill and eat the Gulls themselves; they also devour offal and carrion. The Great Skua is a scarce species, and is but seldom seen round our shores. The only breeding-stations within the United Kingdom are on two islands of the Shetlands, where it is strictly protected. During the winter, unless driven inshore by stress of weather, it keeps out at sea, remaining near the Gulls on the fishing-grounds. The nest is a “scrape” among the heather on the highest part of some island, and the eggs, two in number, are olive brown with darker markings. In defence of their home this species is very bold, sweeping down continually at an intruder and even striking at him with their wings. The sexes are alike, and are dark brown above with chestnut and whitish mottlings; below they are of a uniform rufous brown. The claws are hooked and sharp. Length 21 in.; wing 16 in. The young resemble their parents. THE POMATORHINE SKUA Stercorarius pomatorhinus (Temminck) This bird, especially when immature, is not very rare on our eastern shores during the autumn migration in September and October, a few even wintering off our south coast. On the return migration in spring it is very rarely seen. It breeds in Eastern Siberia and thence eastward across Arctic America to Greenland. The adult has the head sooty black. The hind neck whitish with straw yellow acuminate feathers. Upper parts brown, two central tail feathers longer than the rest and twisted vertically. Under parts whitish, except the flanks and abdomen, which are brown. Length 21 in.; wing 14·25 in. The young bird in its first autumn is brown mottled and barred with dull rufous. It takes more than a year to assume the full adult plumage. THE ARCTIC OR RICHARDSON’S SKUA Stercorarius crepidatus (J. F. Gmelin) This is the commonest of the Skuas, occurring on all the Scottish coasts and being fairly common in the east of England every autumn. In Ireland and the west of England it is only an irregular straggler. It breeds in the Shetlands, Orkneys, and the north of Scotland, some moor at no great distance from the sea being chosen as a summer home. No nest is made, but a depression is formed in the moss or grass on which the two brownish green eggs, blotched with darker brown, are laid. The young when first hatched are covered with dark brown down. In its habits and food it does not differ from the other Skuas.