The great black-backed gull (Larus marinus) is the largest member of the gull and tern family Laridae. It is a very aggressive hunter, pirate and scavenger which breeds on the North Atlantic coasts and islands of northern Europe and northeastern North America. Southern populations are generally sedentary, while those breeding in the far north (northern Norway, northwest Russia) migrate farther south in winter. A few also move inland to large lakes and reservoirs. The adult has a white head, neck and underparts, dark blackish-grey wings and back, pink legs and the bill yellow with a red spot.
Taxonomy
The great black-backed gull was one of the many species originally described by Carl Linnaeus in his 1758 10th edition of Systema Naturae, and it still bears its original scientific name of Larus marinus. or when taken together, "sea gull". The name predates Linnean taxonomy, as it had been called Larus ingens marinus by Carolus Clusius. The species is sometimes referred to as the greater black-backed gull.
Description
This is the largest gull in the world, They will also catch flying passerines, which they typically target while the small birds are exhausted from migration and swallow them immediately.
thumb|right|Adult great black-backed gull steals a bird carcass from a juvenile of the same species, then swallows it whole
Most foods are swallowed whole, including most fish and even other gulls. When foods are too large to be swallowed at once, they will sometimes be shaken in the bill until they fall apart into pieces. Like some other gulls, when capturing molluscs or other hard-surfaced foods such as eggs, they will fly into the air with it and drop it on rocks or hard earth to crack it open. Alternative foods, including berries and insects, are also eaten when available, and they will readily exploit easy food sources, including chum lines made by boats at sea. They are skilled kleptoparasites who will readily pirate fish and other prey captured by other birds, and their size allows them to dominate over other gulls when encountering them. At tern colonies in coastal Maine, American herring gulls (L. smithsonianus) occasionally also attack nestling and fledgling terns but in a great majority of cases their catch were immediately pirated by great black-backs. In one study from Norway, great black-backed gulls were the fifth highest frequency prey item for white-tailed eagles and gulls are prone to mobbing these huge eagles. The great black-backed gull has also been observed engaging in aerial combat with bald eagles, attacking the eagles and chasing them away. A great skua (Stercorarius skua) was filmed in Scotland unsuccessfully attempting to kill a second or third year great black-backed gull.) and harvested for its feathers, which were used in the hat-making trade; as a result the species became locally extinct from particularly southern parts of its range as a result of this exploitation.