Goéland de l'Ouest

Taxonomie

Nom scientifique

Larus occidentalis

Autorité

Audubon, 1839

Ordre

Charadriiformes

Famille

Laridae

Genre

Larus

Répartition et habitat

The western gull is a year-round resident in California, Oregon, Baja California, and southern Washington. It is migratory, moving to northern Washington, British Columbia, and Baja California Sur to spend the nonbreeding season.

Aire de reproduction

NA, MA : w North Pacific coast from nw Washington to I. Guadelupe and c Baja California (nw Mexico)

Aire hors reproduction

to s British Columbia and s Baja California (nw Mexico)

Migration

Complete migrants

Comportement

The western gull rarely ventures more than approximately 100 miles inland, almost never very far from the ocean; it is almost an exclusively marine gull. It nests on offshore islands and rocks along the coast, and on islands inside estuaries. A colony also exists on Ano Nuevo Island, then Anacapa Island and Santa Barbara Island in Channel Islands National Park, and Alcatraz Island in San Francisco Bay. In the colonies, long term pairs aggressively defend territories whose borders may shift slightly from year to year, but are maintained for the life of the male.[citation needed]<p>Western gulls feed in pelagic environments and in intertidal environments. At sea, they take fish and invertebrates like krill, squid and jellyfish. They are unable to dive and feed exclusively on the surface of the water. On land they feed on seal and sea lion carcasses and roadkill, as well as cockles, starfish, limpets and snails in the intertidal zone. They also feed on human food refuse, in human-altered habitats including landfills, and take food given to them, or stolen from people at marinas, beaches and parks. Western gulls are known to be predatory, killing and eating the young of other birds, especially ducklings, and even the adults of some smaller bird species. Western gulls, including one who lived at Oakland's Lake Merritt are known for killing and eating pigeons (rock doves). They will also snatch fish from a cormorant's or pelican's mouth before it is swallowed. The bird has also been observed directly pilfering milk from the elephant seal's teat.

Conservation

Tendance de la population

rising