Glaucous Gull Life History

Habitat

Habitat Shorelines

Glaucous Gulls nest on sea cliffs and coastlines, often near colonies of other birds such as Northern Fulmars, auks, waterfowl, or other gulls. Here, they defend large ledges or other prominences. Some Glaucous Gulls also nest farther inland, usually on predator-free islands in tundra lakes. During the nesting season, they forage along coastlines, in open water, and around sea ice and icebergs. They rest in small groups around ponds and on shorelines, especially gravel islands and bars, mudflats, river mouths, or raised areas of tundra known as hummocks or pingos. Migrants tend to stay near water, but where there is abundant food (such as at a landfill), they often appear inland. Wintering birds use a great variety of habitats, from pelagic (offshore) waters to littoral (coastal) waters, freshwater lakes (including the Great Lakes), harvested agricultural fields, and landfills. In the far north, some forage in pack ice and in polynyas, areas of open water in the pack ice. Human activities such as hunting and fishing attract Glaucous Gulls. They regularly follow fishing vessels in the ocean, waiting for nets to be raised, so they can scavenge fish brought to the surface. They also gather at garbage dumps, fish-processing plants, and sewage outfalls.

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Food

Food Omnivore

Glaucous Gulls are omnivores and opportunists, like all large gulls. For much of the year, they eat marine invertebrates and fish. Their foraging strategies vary, depending on the habitat and prey. In tidal zones, they hunt by walking along shores and mudflats or swimming in water and seizing prey with the bill. In deeper water, they often fly above the water’s surface until spotting prey, then drop onto it to seize it beneath the water. They also eat many kinds of carrion found in the water, on shorelines, or on ice, including the remains of polar bear kills and remains of caribou and whales harvested by humans. At carrion or other attractive food sources (walrus placentas are a favorite), they compete aggressively with other seabirds, ousting all but the larger Great Black-backed Gulls. They take advantage of icebergs that overturn, exposing marine invertebrates on the undersurface. They sometimes follow ships, seals, or whales to feed on bycatch of vessels or scraps of food left from marine mammals’ foraging, and they scavenge at landfills and fish-processing plants. They also hunt small mammals and birds, their young, and eggs: virtually every species of bird that nests in the arctic (or its young) counts as prey, from longspur to murre, ptarmigan to kittiwake. Large males can swallow prey the size of a Long-billed Dowitcher whole. Glaucous Gulls regularly hunt Dovekies at their colonies, from the air and on foot, sometimes waiting near a nest site to ambush adults as they leave. They often fly above arctic foxes that are walking through seabird colonies, then seize young or eggs left unattended during the disturbance. Glaucous Gulls steal fish and other food from adult seabirds returning to colonies to provision young and from foraging loons, mergansers, and other seabirds that bring fish to the surface.

At sea, Glaucous Gulls often join large mixed-species flocks of seabirds, including gulls, auks, eiders, and fulmars, either preying directly on fish or stealing from other seabirds. They also eat insects (flies, beetles, caterpillars), berries (crowberry, lingonberry, cloudberry), marine algae, and human refuse. Prey items include various marine worms (polychaetes), small plankton and crustaceans (isopods, euphausiids, and other zooplankton), goose barnacles, common starfish, green sea urchin, spider crab, green crab, northern horsemussel, blue mussel, arctic cod, cod, sandlance, capelin, dab, sea scorpion, lumpfish, rock gunnel, Atlantic herring, and Pacific herring. Mammal prey includes lemmings (brown lemming, arctic lemming, northern collared lemming), voles (root vole, meadow vole), muskrat, arctic ground-squirrels, arctic shrews, and least weasels.

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Nesting

Nest Placement

Nest Cliff

Nests are set in locations inaccessible to arctic foxes: on high cliff ledges or grassy areas at the tops of cliffs, on small islands in lakes, and other remote settings.

Nest Description

Both male and female construct the nest, a shallow depression made of grass, sedges, moss, seaweed, twigs, and occasionally feathers. Nests average about 18 inches across, with interior cup about 12 inches across and 4 inches deep. Adults add to the nest through the season, and some nests become much larger.

Nesting Facts
Clutch Size:1-3 eggs
Egg Description:

Light gray-brown or olive with gray and dark brown spots.

Condition at Hatching:

Alert and mobile, covered with dense, hairlike, gray-brown down.

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Behavior

Behavior Ground Forager

Glaucous Gulls are monogamous in their mating system; studies of marked birds indicate that mated pairs reunite annually at the same nesting site for many years in a row. Because of this mating system, “new” courtship displays are seldom observed. In early spring, unmated males form groups that gather in coastal areas. Unmated females visit these “clubs” and select a mate by walking around a male with head drawn in, giving a high-pitched call and raising the bill quickly. How the pair selects the nest site is unknown. Pairs may nest solitarily or in colonies of up to a few dozen pairs. Both adults defend their nest area, particularly after chicks are hatched, driving out others of their species and any potential predator or warning them away with threat displays. They also defend a foraging territory near the nest, particularly when it is located by a seabird colony. Away from the nest area, Glaucous Gulls are gregarious, gathering in flocks to feed, rest, and preen, although among foraging birds, conflict over food can be almost constant. Wintering birds regularly join large assemblages of gulls and other water birds, where they are dominant over virtually every other species except Great Black-backed Gull, the only gull species in the world that is larger.

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Conservation

Conservation Low Concern

Glaucous Gull populations appear to be stable. Partners in Flight estimates a global breeding population of 910,000 birds and rates the species a 7 out of 20 on the Continental Concern Score, indicating a low level of conservation concern. In 2002, the North American Waterbird Conservation Plan estimated 169,200 breeding birds on the continent. As is true of other top arctic predators such as polar bears, Glaucous Gulls in some regions have high levels of organochlorines, PCBs, mercury, and other toxic contaminants known to harm reproduction. In Greenland and Russia, Glaucous Gulls are killed to keep populations of eiders higher, and this culling practice could also have negative impacts on populations.

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Credits

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.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.

Weiser, Emily and H. Grant Gilchrist. (2012). Glaucous Gull (Larus hyperboreus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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