In the Antarctic Victoria Land occurs a paler form, _M. maccormicki_. _Stercorarius pomatorhinus_, the Pomatorhine Skua, breeds on the tundras of Siberia and possibly from Greenland to Bering Sea, migrating to Britain and as far as South Africa, North Australia, and Peru. The plumage is brown, with blacker head and gorget, white breast, and acuminate white neck-feathers tipped with yellow. The projecting median rectrices with their vertically twisted vanes are mentioned above (p. 301). Uniform brown specimens may be immature. _S. crepidatus_, the Arctic Skua, is smaller, and nests as far south as Northern and Western Scotland, but properly occupies Arctic and sub-Arctic Europe, Asia, and America; in winter, it reaches South Africa, Australia, New Zealand, and Brazil. The elongated rectrices are not twisted, but are pointed, while a uniform dark phase–the true _S. richardsoni_–is common to both sexes. _S. parasiticus_, Buffon's Skua, distinguished from the last-named by its extremely prolonged rectrices and greyer upper surface, breeds on the Scandinavian fells and throughout the Arctic tundras and barren grounds, migrating as far south as Gibraltar and lat. 40° N. in America. The habits of the members of this genus are similar to those of _Megalestris_, but their quicker flight enables them to rob even Terns, and the mewing cry is most peculiar, while the eggs are intermediate in style between those of Whimbrels and Gulls. These small Skuas often destroy Lemmings. Sub-fam. 2. _Larinae._–_Rissa tridactyla_, the Kittiwake, breeds from the circumpolar regions southwards to the Kuril Islands, the Gulf of St. Lawrence, and North-West France; in winter it reaches western North America, the Bermudas, the Canaries, the Mediterranean, and the Caspian. The feet are black, the hind-toe is absent or rudimentary. From _Larus canus_, which it closely resembles when flying, it can be distinguished by the absence of white spots at the ends of the primaries. The young bird, or {306}Tarrock, is much variegated with dark grey or black, and has a blackish tip to the tail, as is the case in most fresh-water Gulls. Many fine colonies inhabit the loftier cliffs of Great Britain, the nests of sea-weed and grass being closely crowded together, and the eggs exhibiting softer colours than is usual in the Sub-family. The darker _R. brevirostris_ of Bering Sea has red feet. _Pagophila eburnea_, the Ivory Gull, seems truly circumpolar, while it accidentally visits Britain, Northern Europe, and New Brunswick. It is pure white, with black feet, the young shewing grey and black variations. It will eat whale- or seal-offal.