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Western gull
The western gull (Larus occidentalis) is a large white-headed gull that lives on the west coast of North America and the Pacific Ocean. The western gull ranges from British Columbia, Canada, to Baja California, Mexico.
It was previously considered conspecific with the yellow-footed gull (Larus livens) of the Gulf of California.
The western gull is a large gull that can measure 55 to 68 cm (22 to 27 in) in total length, spans 130 to 144 cm (51 to 57 in) across the wings, and weighs 800 to 1,400 g (1.8 to 3.1 lb). The average mass among a survey of 48 gulls of the species was 1,011 g (2.229 lb). Among standard measurements, the wing chord is 38 to 44.8 cm (15.0 to 17.6 in), the bill is 4.7 to 6.2 cm (1.9 to 2.4 in) and the tarsus is 5.8 to 7.5 cm (2.3 to 3.0 in). The western gull has a white head and body, and upperparts or mantle is dark grey. The head generally remains white year-round, developing little to no streaking patterns in northern populations during the nonbreeding phase (basic plumage). It is debatable the extent of head markings can be found in pure Western Gulls as they form a hybrid zone with the glaucous-winged gull (Larus glaucescens) which has a more extensive hood. It has a large and bulbous-tipped yellow bill with a red subterminal spot (this is the small spot near the end of the bill that chicks peck in order to stimulate feeding). The eye colour varies, averaging pale yellow in southern populations and darker in northern populations. It closely resembles the slaty-backed gull (Larus schistisagus) of Asia, but the latter species has paler eyes, a straighter bill, deeper pink legs and eye orbitals, as well as conspicuous white spots ("string of pearls") on the inner primaries when seen in flight not seen in Western Gulls. Western gulls take approximately four years to reach their full plumage, their layer of feathers and the patterns and colors on the feathers. In adult plumage, The largest western gull colony is on the Farallon Islands, located about 26 mi (40 km) west of San Francisco, California; an estimated 30,000 gulls live in the San Francisco Bay area. Western gulls also live in the Oregon Coast.
Two subspecies are recognized, differentiated by the mantle and eye colouration. The northern subspecies L. o. occidentalis is found between Central Washington and Central California, has dark grey upperparts. The southern subspecies L. o. wymani is found between central and southern California has a darker mantle (approaching that of the Great black-backed gull) and has paler eyes on average. wymani has more advanced plumage development than occidentalis, and generally attains adult plumage by the third year.
The call of the Western gull is bright, piercing, and repetitive.
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.
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]
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.
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Western gull
The western gull (Larus occidentalis) is a large white-headed gull that lives on the west coast of North America and the Pacific Ocean. The western gull ranges from British Columbia, Canada, to Baja California, Mexico.
It was previously considered conspecific with the yellow-footed gull (Larus livens) of the Gulf of California.
The western gull is a large gull that can measure 55 to 68 cm (22 to 27 in) in total length, spans 130 to 144 cm (51 to 57 in) across the wings, and weighs 800 to 1,400 g (1.8 to 3.1 lb). The average mass among a survey of 48 gulls of the species was 1,011 g (2.229 lb). Among standard measurements, the wing chord is 38 to 44.8 cm (15.0 to 17.6 in), the bill is 4.7 to 6.2 cm (1.9 to 2.4 in) and the tarsus is 5.8 to 7.5 cm (2.3 to 3.0 in). The western gull has a white head and body, and upperparts or mantle is dark grey. The head generally remains white year-round, developing little to no streaking patterns in northern populations during the nonbreeding phase (basic plumage). It is debatable the extent of head markings can be found in pure Western Gulls as they form a hybrid zone with the glaucous-winged gull (Larus glaucescens) which has a more extensive hood. It has a large and bulbous-tipped yellow bill with a red subterminal spot (this is the small spot near the end of the bill that chicks peck in order to stimulate feeding). The eye colour varies, averaging pale yellow in southern populations and darker in northern populations. It closely resembles the slaty-backed gull (Larus schistisagus) of Asia, but the latter species has paler eyes, a straighter bill, deeper pink legs and eye orbitals, as well as conspicuous white spots ("string of pearls") on the inner primaries when seen in flight not seen in Western Gulls. Western gulls take approximately four years to reach their full plumage, their layer of feathers and the patterns and colors on the feathers. In adult plumage, The largest western gull colony is on the Farallon Islands, located about 26 mi (40 km) west of San Francisco, California; an estimated 30,000 gulls live in the San Francisco Bay area. Western gulls also live in the Oregon Coast.
Two subspecies are recognized, differentiated by the mantle and eye colouration. The northern subspecies L. o. occidentalis is found between Central Washington and Central California, has dark grey upperparts. The southern subspecies L. o. wymani is found between central and southern California has a darker mantle (approaching that of the Great black-backed gull) and has paler eyes on average. wymani has more advanced plumage development than occidentalis, and generally attains adult plumage by the third year.
The call of the Western gull is bright, piercing, and repetitive.
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.
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]
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.