Great Black-backed Gull
The Great Black-backed Gull is North America's largest and heaviest gull. Increasingly common throughout their range in eastern North America, Great Black-backed Gulls are generally easy to distinguish from other gulls by their massive proportions and their black mantles.

Great Black-backed Gulls breed along the Atlantic coast of North America, from Labrador to North Carolina, particularly on islands offshore. They also breed along St. Lawrence River, on the northern shore of Lake Ontario, and at one site on the eastern shore of Lake Huron. Great Black-backed Gulls strongly prefer breeding sites that are isolated from terrestrial predators; they may be found breeding on barrier beaches and in salt marshes, as well as on islands.

The species is partially migratory. Great Black-backed Gulls breeding in Nova Scotia and southern locations do not migrate, while others from northern parts of the breeding range disperse southward in winter to the mid-Atlantic coast or the Great Lakes. Some Great Black-backed Gulls may also be found in winter on smaller inland bodies of water in New Jersey, New York, and New England.

Great Black-backed Gulls also breed on Greenland and on the coasts and islands of the northeast Atlantic, the North Sea, the Baltic Sea, and the Barents Sea. Individuals breeding in Greenland and Europe winter on the shores of Western Europe and the Mediterranean, Black, and Caspian seas.
Great Black-backed Gull Range Map

The diet of Great Black-backed Gulls includes fish; marine and intertidal invertebrates; small mammals; insects; and eggs, chicks, and adult birds (including waterfowl). They steal food from other seabirds, and even from Bald Eagles and sharks. Great Black-backed Gulls also scavenge carrion and human-created garbage.

Great Black-backed Gulls can drink salt water. They, like other marine gulls, possess special glands over their eyes, with minute tubules that extract salt from blood. Fluid containing the extracted salt drips out through the nostrils; it is about twice as concentrated as urine. Great Black-backed Gulls also regularly visit bodies of fresh water to drink, when possible.

Great Black-backed Gulls are almost exclusively monogamous. They breed in single pairs or in loose colonies. Pairs form on the breeding grounds in March and April, with laying of first eggs generally in late April or early May. Nests consist of scrapes in ground, lined with feathers, vegetation, and other small pieces of debris; pairs may start but not finish other nests on their territory. Most clutches contain three eggs. Both parents incubate eggs and brood and feed nestlings.

During the 19th century, Great Black-backed Gulls suffered severe population declines in North America as a result of hunting and egg collection by humans. Populations in North America have recovered under legal protection since the early 20th century; now, Great Black-backed Gull populations may exceed all past historical levels, and their breeding range appears to be expanding southward.

Description: Adult Great Black-backed Gulls are white with slate-black backs and wings. Bills are yellow with a red dot near the tip of the lower mandible. Iris is gray or pale yellow. Legs are pale pink. The very tips of the wings are completely white; this characteristic can help distinguish Greater Black-backed Gull from similarly large and dark gulls, including Western.

Length is about 30 inches from bill to tail. Great Black-backed Gulls appear large and stocky. Size difference is often obvious when they are in the company of other gulls, though a few light-colored gulls (Herring, Glaucous, Glaucous-winged) can attain similar dimensions.

Great Black-backed Gulls attain adult plumage by their fourth year of life. First-year birds are nearly as large as adults, with mostly white heads and breasts, and barred or checkered back and wings. Bill is black. White rump and dark band at tip of tail are often visible when bird is in flight. Second-year birds resemble first-year birds, but with yellow bill encircled by a black band, near the tip. Third-year Great Black-backed Gulls generally resemble adults in general plumage coloration, but have a black ring on the bill, as second-year birds do.

Voice: Calls resemble those of Herring Gull (a trumpeted "keow"), but are hoarser and much lower in pitch. Calls have subtle differences depending on the bird's posture, or are particular to specific behavioral acts.


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