Great Black-backed Gulls forage widely over the ocean, along shorelines, and at landfills and fishing docks. They rest or “loaf” in open areas such as parking lots, fields, runways, and piers. They breed in isolated places safe from terrestrial predators, such as small islands, rocky islets, saltmarshes, and barrier beaches. They nest in relatively high, open habitat close to the water, with some vegetation for cover. During the winter Great Black-backed Gulls move more widely along the Atlantic coast and may travel inland along major rivers. Back to top
Great Black-backed Gulls hunt mussels, crabs, sea urchins, other marine invertebrates, fish and birds. They also scavenge dead fish, carrion, and trash, and steal food from other animals (including diving ducks, terns, puffins, murres, shorebirds, eagles, and sharks). Along rocky shores, Great Black-backed Gulls forage for invertebrates in shallow water. On mudflats they follow the retreating tide to capture worms and small bivalves. At sea they congregate around upwellings with concentrated prey or follow fishing boats. They also forage at garbage dumps, more so during the winter than during the breeding season. Great Black-backed Gulls eat eggs, chicks, and adults of other birds, including Atlantic Puffins, Common Murres, Herring Gulls, Common Terns, Roseate Terns, Manx Shearwaters, Horned Grebes, and migrant songbirds.Back to top
Great Black-backed Gulls nest on rocky outcrops, grassy knolls, barrier island dunes, and other sites above the reach of the tide. Nests are usually next to large objects such as logs, bushes, or rocks, which provide a windbreak and a visual screen from the neighbors. Each pair starts several nests, and the final site is determined by where the female lays her eggs. The pair reuses the same site, but not the nest itself, in subsequent years.
The male and the female both dig several scrapes, filling them with vegetation, feathers, rope, plastic, and other materials. The female chooses one of these sites for laying her eggs. The nest is 8–20 inches wide, while the inner cup is 5–13 inches across and 2-4 inches deep.
|Clutch Size:||2-3 eggs|
|Number of Broods:||1 brood|
|Egg Length:||2.8-3.4 in (7.1-8.5 cm)|
|Egg Width:||2.0-2.3 in (5.1-5.8 cm)|
|Incubation Period:||30-32 days|
|Nestling Period:||1 day|
|Egg Description:||Pale yellowish, greenish, or brownish, with speckles of dark brown or olive.|
|Condition at Hatching:||Fairly active, with open eyes, and covered in thick gray down with black spots; ready to leave nest within 24 hours.|
Great Black-backed Gulls nest on their own or in loose colonies, sometimes with other gulls, terns, skimmers, auks, and eiders, and rarely with cormorants and gannets. The male establishes a small breeding territory, 10 to 20 feet in diameter, and the pair defends it against other gulls. Great Black-backed Gulls are monogamous and return to the same territory year after year. When pairing, a male displays and calls to attract a female, leaning forward with his head bent toward the ground and mewing; or flying slowly with exaggerated wingbeats. The female may join him. Courting males sometimes regurgitate food for females. Aggressive individuals crouch low and jab their bill at an opponent, or pull at vegetation. They also stand, lean far forward, then throw back their head and give a long series of cries. After chicks hatch the parents become especially aggressive. When terrestrial predators approach, the gulls dive and strike with their feet or wings, or rarely with their bills. Lost chicks that stray onto an unfamiliar territory may find themselves seized by the head and shaken, or even eaten. Chicks leave the nest within 24 hours but stay in the nesting territory for 40 days. They begin to fly at 45 days but return to the territory for feedings from their parents for another 3-4 weeks. Egg predators include various gull species, ravens, crows, raccoons, and rats. Bald Eagles, Common Ravens, dogs, cats, and other gulls sometimes prey on the chicks. Back to top
Great Black-backed Gulls are numerous on the East Coast, however, since 1966 populations have been declining according to the North American Breeding Bird Survey. For example, between 1966 and 2015, populations in Maine declined by over 8.5% per year resulting in a cumulative loss of 99% of the population. The North American Waterbird Conservation Plan estimates a total of 121,430 breeding birds on the continent. The species rates a 12 out of 20 on the Continental Concern Score, and is not on the 2016 State of North America's Birds' Watch List. Nineteenth-century feather hunters and egg collectors nearly drove the North American population of Great Black-backed Gulls to extinction. Thanks to legal protection, the population recovered during the twentieth century and perhaps exceeded its historical size by the 1960s. Taking advantage of landfills, fishing discards, and other human-made food sources, the gulls continued to increase in numbers as they expanded south into Maryland, Virginia, and North Carolina. They have displaced Herring Gulls from some breeding habitats in New England. Management officials control the breeding Great Black-backed Gull populations on some islands to give terns, puffins, and other gull species a chance to nest.Back to top
Good, Thomas P. (1998). Great Black-backed Gull (Larus marinus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.
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Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.