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Larus glaucescensglaucous-winged gull

By Timon Bullard

Geographic Range

Larus glaucescens nests on rocky cliffs among the seabird colonies of the coastal northern Pacific, from Alaska and the Aleutians south to northern Washington state. Winters from southern Alaska to south along the Pacific coast as far as Baja California, occasionally in the eastern Hawaiian islands (Godfrey 1986).

Habitat

L. glaucescens lives primarily in the vicinity of salt or brackish water along coasts: bays, estuaries, islands, beaches, mud flats, and nearby offshore. It can also be found around wharves, dumps, fish canneries, and fishing boats. It sometimes follows rivers, but is not normally found very far inland (Godfrey 1986).

Physical Description

Adults of L. glaucescens have a body length of 24-27 inches, and a wingspan of around 54 inches, males larger than females. Adults are white with a pale grey back (hence specific name glaucescens: Latin for greying, from Greek glaukos, blue-grey). Wings are also pale grey, with small white patches. Large, heavy yellow bill with red spot. Skin around eyes purplish pink, iris silver to yellow powdered with brown, giving a dark appearance. Juvenile birds have a dark bill, and mottled grey plumage (Hoffman et al. 1978; Godfrey 1986)

  • Average mass
    908 g
    32.00 oz
    AnAge

Reproduction

L. glaucescens nests in large colonies, especially in Alaska, but also in smaller colonies to the south. Adult birds frequently return to the same colony year after year, often re-pairing with a mate from the previous year. The nest is a mound of dried plants and seaweed, sometimes fish bones and feathers, built amongst ground cover of low islands or rocky ledges of higher islands or headlands. A single brood is laid from late May to July, consisting of 2-3 buff or olive-buff eggs marked with darker brown spots. The eggs are incubated for 26-28 days. Chicks are first capable of flight around 35-54 days after hatching, attaining a fully adult plumage in the fourth year. Individual birds have been observed to live for twenty years (Campbell 1968; Murphy et al. 1984; Verbeek 1985).

  • Average eggs per season
    3
    AnAge
  • Average time to hatching
    27 days
    AnAge

Lifespan/Longevity

Behavior

L. glaucescens is territorial upon the breeding grounds, resulting in frequent squabbles between adult birds, most often the males. It is gregarious throughout the year, even with different gull species. Calls are described as similar to those of the Herring Gull (L. argentatus), involving a variety of prolonged wails, chuckles, and hisses, as well as the food-begging calls of young birds. The red spot on the adult bill is believed to stimulate a pecking response from the young chicks, which in turn causes the parent to regurgitate food for the chick (Verbeek 1985; Godfrey 1986).

Communication and Perception

Food Habits

L. glaucescens is omnivorous, feeding on carrion, fish, invertebrates, seaweed, and food stolen from other marine birds (pelicans, cormorants, sea ducks). During periods of lowest tidal heights mussels and barnacles comprise much of their diet, but at other times sea urchins, chitons, and limpets are preferentially gathered. Barnacles, sea urchins, molluscs, and other resistant food items are gathered from the shore and dropped onto rocks from the air to crack them open. In the vicinity of humans L. glaucescens will scavenge garbage from docks, dumps, and shores, and follow fishing vessels. It may also forage over the open ocean, but rarely to more than a few miles offshore (Murphy et al. 1984; Irons et al. 1986).

Economic Importance for Humans: Negative

Being a scavenger on human wastes, L. glaucescens can be considered a pest in areas of high population, but never to any harmful level.

Conservation Status

L. glaucescens winters in coastal Pacific waters to the southern Baja, and though it is not threatened in any of these areas it is protected under the U.S. Migratory Bird Treaty Act. The population of L. glaucescens has increased around three and a half times in the last 50 years, mostly due to accessibility of human wastes (Verbeek 1985).

Other Comments

Interbreeding between L. glaucescens and the Herring Gull is common and widespread in Alaska, and a single mating pair of these species was known from Okanagan Lake, British Columbia. L. glaucescens also hybridises with the Western Gull (L. occidentalis) along the coast of Oregon and Washington states (Williamson and Peyton 1963; Merilee 1974; Hoffman et al. 1978).

Contributors

Timon Bullard (author), University of Alberta, Cindy Paszkowski (editor), University of Alberta.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Campbell, R. 1968. Notes on a twenty-year-old Glaucous-winged Gull. Bird Banding, 39: 226-227.

Godfrey, W. 1986. The birds of Canada. Ottawa: National Museum of Natural Sciences.

Irons, D., R. Anthony, J. Estes. 1986. Foraging strategies of Glaucous-winged Gulls in a rocky intertidal community. Ecology, 67: 1460-1474.

Merilees, W. 1974. A Glaucous-winged Gull mated to a Herring Gull on Okanagan Lake, British Columbia. Canadian Field-Naturalist, 88: 485-486.

Murphy, E., R. Day, K. Oakley, A. Hoover. 1984. Dietary changes and poor reproductive performance in Glaucous-winged Gulls. Auk, 101: 532-541.

Verbeek, N. 1985. Aspects of the breeding biology of an expanded population of Glaucous-winged Gulls in British Columbia. Journal of Field Ornithology, 57: 22-33.

Williamson, F., L. Peyton. 1963. Interbreeding of Glaucous-winged and Herring Gulls in the Cook Inlet region, Alaska. Condor, 65: 24-28.

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