The great black-backed gull (Larus marinus), also known as the greater black-backed gull or, informally, as the black-back, is the largest member of the gull family. It breeds on the European and North American coasts and islands of the North Atlantic and is fairly sedentary, though some black-backs move farther south or inland to large lakes or reservoirs. The adult great black-backed gull has a white head, neck and underparts, dark grey wings and back, pink legs and yellow bill.
The great black-backed gull was one of the many species originally described by Linnaeus in his 18th-century work, Systema Naturae, and it still bears its original name of Larus marinus.
The adult great black-backed gull is fairly distinctive, as no other very large gull with blackish coloration on its upper-wings generally occurs in the North Atlantic. In other white-headed North Atlantic gulls, the mantle is generally a lighter gray color and, in some species, it is a light powdery color or even pinkish. It is grayish-black on the wings and back, with conspicuous, contrasting white “mirrors” at the wing tips. The legs are pinkish, and the bill is yellow or yellow-pink with some orange or red near tip of lower bill.