Great Black-backed Gull

The Great Black-backed Gull is the largest gull species in the world, a powerful and imposing bird of North Atlantic coastlines recognized by its very dark, almost black back and wing feathers contrasting sharply with a white head and underparts. Unlike many gulls that rely mostly on scavenging, this species is also an active predator, taking eggs, chicks, and even adult birds of other species.

Adult mantle and back feathers are a very dark slate-black, among the darkest of any gull species, providing strong contrast with the clean white head, neck, and underparts feathers. The outer primary flight feathers are black with white tips and a small white mirror, the black blending closely with the already dark mantle so the wingtip pattern is less strikingly separate than in paler-backed gulls. Immature birds show a checkered pattern of blackish-brown and white or buff feathers, notably bold and contrasty compared to the browner, less checkered pattern of immature Herring Gull. This is a four-year gull, with the back feathers darkening progressively with each successive plumage until the full black adult mantle is reached.

Sexes look alike, with males averaging larger and more powerfully built. This is a four-year gull, requiring about four years to reach full adult black-backed plumage, with immature plumages showing a strongly checkered blackish-brown-and-white pattern that is bolder than the messier mottled brown of similarly aged Herring Gulls. Nonbreeding adults show little to no head streaking, keeping a largely clean white head year-round, unlike many other large gulls. A complete post-breeding molt replaces flight feathers over an extended period.

Breeds along rocky coastlines, cliffs, and offshore islands of the North Atlantic, including eastern North America, Iceland, and western Europe. It forages over open coastal and offshore waters, harbors, and beaches, and while some northern populations move south in winter, many individuals remain in coastal areas year-round.

Great Black-backed Gulls are powerful, opportunistic feeders, taking fish, marine invertebrates, carrion, and refuse, but are also notable active predators of eggs, chicks, and small to medium-sized adult birds, including other seabirds. Nests are built on the ground on cliffs, offshore islands, or open coastal habitat, often in loose colonies or as isolated pairs, with both parents sharing incubation and chick defense. The call is a deep, gruff series of notes, lower-pitched than smaller gull species. Conservation status is IUCN Least Concern.