Western gull

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Western gull
Larus occidentalis (Western Gull), Point Lobos, CA, US - May 2013.jpg
Adult
Larus occidentalis6.jpg
Juvenile (1st Winter)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Class: Aves
Order: Charadriiformes
Family: Laridae
Genus: Larus
Species:
L. occidentalis
Binomial name
Larus occidentalis
Audubon, 1839
Larus occidentalis map.svg
Distribution
  Year-round
  Nonbreeding

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. [2]

Contents

It was previously considered conspecific with the yellow-footed gull (Larus livens) of the Gulf of California.

Physical description

Western Gull in flight over the cliffs of Bodega Head Larus occidentalis in flight (Bodeda Head).jpg
Western Gull in flight over the cliffs of Bodega Head

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). [3] [4] The average mass among a survey of 48 gulls of the species was 1,011 g (2.229 lb). [5] 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). [3] 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 in northern populations. 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 and deeper pink legs and eye orbitals. In the north of its range it forms a hybrid zone with its close relative the glaucous-winged gull (Larus glaucescens). Western gulls take approximately four years to reach their full plumage, [6] 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; [7] an estimated 30,000 gulls live in the San Francisco Bay area. Western gulls also live in the Oregon Coast. [8]

Two subspecies are recognized, differentiated by the mantle and eye colouration. [9] 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. [3]

Auditory description

The call of the Western gull is bright, piercing, and repetitive.

Distribution and 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.

Behavior

Pair-bonding behaviour Larus occidentalis - pair bonding behaviour.jpg
Pair-bonding behaviour

The western gull rarely ventures more than approximately 100 miles inland, almost never very far from the ocean; [6] 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 ]

Feeding

Western gulls feed in pelagic environments and in intertidal environments. At sea, they take fish [7] 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. [10]

Reproduction

A nest of vegetation is constructed inside the parent's territory and 3 eggs are laid. These eggs are incubated for a month. The chicks, once hatched, remain inside the territory until they have fledged. Chicks straying into the territory of another gull are liable to be killed by that territory's pair. Chick mortality is high, with on average one chick surviving to fledging. On occasion, abandoned chicks will be adopted by other gulls.

Hybridization

Between Puget Sound in Washington and Northern Oregon, the western gull hybridizes frequently with the glaucous-winged gull, a cross referred to as the Olympic gull. [9] Hybrids between the two species are variable and may features of either parent species, they have paler mantles and wingtips paler than Western gulls but darker than Glaucous-winged gulls. Additionally, the nonbreeding plumage of hybrids typically has darker head markings than pure Western gulls, which have little to no streaking in their nonbreeding plumage. [3]

The prevalence of 'Olympic gull' hybrids is an example of bounded hybrid superiority, where natural selection favours hybrids in areas of intermediate habitat. One study found that females paired with hybrid males have higher breeding success than pairs of the same species. [11] In the central part of the hybrid zone, clutch size was larger among pairs with hybrid males, many of which established breeding grounds in more vegetative cover than pure western gull males, which preferred sand habitat resulting in heavier predation. In the northern section of the hybrid zone, there was no difference in clutch size, but breeding success is higher due to the hybrids being more similar to western gulls in foraging behaviour, feeding more on fish than glaucous-winged gulls. Little evidence of assortative mating was observed, except for weak assortative mating among hybrids in absence of mixed species pairs.

Western gulls and humans

Over San Francisco Bay Larus Occidentalis - San Francisco.JPG
Over San Francisco Bay

The western gull is currently not considered threatened. However, they have, for a gull, a restricted range. Numbers were greatly reduced in the 19th century by the taking of seabird eggs for the growing city of San Francisco. Western gull colonies also suffered from disturbance where they were turned into lighthouse stations, or, in the case of Alcatraz, a prison.

Western gulls are very aggressive when defending their territories and consequently were persecuted by some as a menace. The automation of lighthouses and the closing of Alcatraz Prison allowed the species to reclaim parts of its range. They are currently vulnerable to climatic events like El Niño events and oil spills.

Thousands of western gulls and chicks reside at the Anacapa Island in Channel Islands National Park.

Western gulls have become a serious nuisance to the San Francisco Giants baseball team. Thousands of gulls fly over Oracle Park in San Francisco during late innings of games. They swarm the field, defecate on fans, and after games eat leftovers of stadium food in the seats; how the birds know when games are about to end is unknown. The gulls left while a red-tailed hawk visited the park in late 2011, but returned after the hawk disappeared. Federal law prohibits shooting the birds, and hiring a falconer would cost the Giants $8000 a game. [8]

Western gull x Glaucous-winged gull hybrid nesting in Oregon. Note the grey (not black) wingtips and paler mantle compared to a pure Western gull. Olympic Gull on nest, western Oregon.jpg
Western gull x Glaucous-winged gull hybrid nesting in Oregon. Note the grey (not black) wingtips and paler mantle compared to a pure Western gull.

In media

The western gull was one of the antagonists in Alfred Hitchcock's famous movie The Birds which was filmed in Bodega Bay, California.

Related Research Articles

<span class="mw-page-title-main">Gull</span> Seabirds of the family Laridae in the suborder Lari

Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, most gulls were placed in the genus Larus, but that arrangement is now considered polyphyletic, leading to the resurrection of several genera. An older name for gulls is mews, which is cognate with German Möwe, Danish måge, Swedish mås, Dutch meeuw, Norwegian måke/måse and French mouette, and can still be found in certain regional dialects.

<span class="mw-page-title-main">Mediterranean gull</span> Species of bird

The Mediterranean gull is a small gull. The scientific name is from Ancient Greek. The genus Ichthyaetus is from ikhthus, "fish", and aetos, "eagle", and the specific melanocephalus is from melas, "black", and -kephalos "-headed".

<span class="mw-page-title-main">Common gull</span> Species of bird

The common gull or sea mew is a medium-sized gull that breeds in the Palearctic. The closely related short-billed gull is sometimes included in this species, which may be known collectively as "mew gull". Many common gulls migrate further south in winter. There are differing accounts as to how the species acquired its vernacular name.

<span class="mw-page-title-main">European herring gull</span> Species of bird

The European herring gull is a large gull, up to 66 cm (26 in) long. Common in coastal regions of Western Europe, it was historically more abundant. It breeds across Northern Europe, Western Europe, Central Europe, Eastern Europe, Scandinavia, and the Baltic states. Some European herring gulls, especially those resident in colder areas, migrate further south in winter, but many are permanent residents, such as in Ireland, Britain, Iceland, or on the North Sea shores. They have a varied diet, including fish, crustaceans, as well as some plants, and are also scavengers, consuming carrion and food left by or stolen from humans.

<span class="mw-page-title-main">Great black-backed gull</span> Species of bird

The great black-backed gull is the largest member of the gull family. Described by the Cornell Lab of Ornithology as "the king of the Atlantic waterfront", it is a very aggressive hunter, pirate, and scavenger. It breeds on the European and North American coasts and islands of the North Atlantic and is fairly sedentary, though some move farther south or inland to large lakes or reservoirs. The adult great black-backed gull has a white head, neck and underparts, dark grey wings and back, pink legs and yellow bill.

<span class="mw-page-title-main">Lesser black-backed gull</span> Species of bird

The lesser black-backed gull is a large gull that breeds on the Atlantic coasts of Europe. It is migratory, wintering from the British Isles south to West Africa. It has increased dramatically in North America, most common along the east coast. Formerly just a winter visitor, many birds are now spotted year-round. Some winters they occur in large numbers. Even on the west coast, this species has become an annual winter visitor in California with birds reported around most of the state each winter. They've even been seen in numbers at the Salton Sea. There is now serious concern about declines in many parts of the species range. The species is now on the RSPB Amber List because the UK is home to 40 per cent of the European population and more than half of these are found at fewer than ten sites.

<span class="mw-page-title-main">Glaucous gull</span> Species of bird

The glaucous gull is a large gull, the second-largest gull in the world. The genus name is from Latin larus, which appears to have referred to a gull or other large seabird. The specific name hyperboreus is Latin for "northern" from the Ancient Greek Huperboreoi people from the far north "Glaucous" is from Latin glaucus and denotes the grey colour of the gull. An older English name for this species is burgomaster.

<span class="mw-page-title-main">Iceland gull</span> Species of bird in the genus Larus

The Iceland gull is a medium-sized gull that breeds in the Arctic regions of Canada and Greenland, but not in Iceland, where it is only seen during winter. The genus name is from Latin larus, which appears to have referred to a gull or other large seabird. The specific name glaucoides denotes its resemblance to Larus glaucus, a synonym of Larus hyperboreus, the glaucous gull; -oides is Ancient Greek and means "resembling".

<span class="mw-page-title-main">Caspian gull</span> Species of bird

The Caspian gull is a large gull and a member of the herring and lesser black-backed gull complex. The scientific name is from Latin. Larus appears to have referred to a gull or other large seabird, and cachinnans means 'laughing', from cachinnare 'to laugh'.

<span class="mw-page-title-main">California gull</span> Species of bird

The California gull is a medium-sized gull, smaller on average than the herring gull, but larger on average than the ring-billed gull. It lives not just in California, but up and down the entire Western coast of North America, and has breeding ground inland. The yellow bill has a black ring.

<span class="mw-page-title-main">Kelp gull</span> Species of bird

The kelp gull, also known as the Dominican gull, is a gull that breeds on coasts and islands through much of the Southern Hemisphere. The nominate L. d. dominicanus is the subspecies found around South America, parts of Australia, and New Zealand. L. d. vetula is a subspecies occurring around Southern Africa.

<span class="mw-page-title-main">Heermann's gull</span> Species of bird

Heermann's gull is a gull resident in the United States, Mexico and extreme southwestern British Columbia, nearly all nesting on Isla Rasa in the Gulf of California. They are usually found near shores or well out to sea, very rarely inland. The species is named after Adolphus Lewis Heermann, nineteenth-century explorer and naturalist.

<span class="mw-page-title-main">Yellow-footed gull</span> Species of bird

The yellow-footed gull is a large gull, closely related to the western gull and thought to be a subspecies until the 1960s. It is endemic to the Gulf of California.

<span class="mw-page-title-main">Slaty-backed gull</span> Species of bird

The slaty-backed gull is a large, white-headed gull that breeds on the north-eastern coast of the Palearctic, but travels widely during nonbreeding seasons. It is similar in appearance to the western gull and the glaucous-winged gull. Another alternate name is Pacific gull, though it also applies to a Southern Hemisphere species, L. pacificus.

<span class="mw-page-title-main">Glaucous-winged gull</span> Species of bird

The glaucous-winged gull is a large, white-headed gull. The genus name is from Latin Larus which appears to have referred to a gull or other large seabird. The specific glaucescens is Neo-Latin for "glaucous" from the Ancient Greek, glaukos, denoting the grey color of its wings.

<span class="mw-page-title-main">Thayer's gull</span> Subspecies of bird

Thayer's gull is a subspecies of the Iceland gull. It is a large gull native to North America.

<span class="mw-page-title-main">Kumlien's gull</span> Subspecies of bird

Kumlien's gull is a subspecies of the Iceland gull. It is a large gull which breeds in the Arctic regions of Canada. It is migratory, wintering from Labrador south to New England and west across the Great Lakes. The subspecies is named after the naturalist Ludwig Kumlien. It is a regular vagrant in small numbers to Britain and Ireland.

<span class="mw-page-title-main">Belcher's gull</span> Species of bird

Belcher's gull, also known as the band-tailed gull, is a bird in the family Laridae found along the Pacific coast of South America. It formerly included the very similar Olrog's gull as a subspecies, but that bird occurs on the Atlantic coast of South America and is now accepted as Larus atlanticus. Belcher's gull is a medium-sized gull with a blackish mantle, white head and underparts, a black band on the otherwise white tail, and a yellow bill with a red and black tip. Non-breeding adults have a brownish-black head and a white eye-ring. The name of this bird commemorates the British explorer Sir Edward Belcher who performed survey work on the Pacific coast of South America.

<span class="mw-page-title-main">Andean gull</span> Species of bird

The Andean gull is a species in subfamily Larinae of the family Laridae, the gulls, terns, and skimmers. It is found in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru.

<span class="mw-page-title-main">American herring gull</span> Species of bird

The American herring gull or Smithsonian gull is a large gull that breeds in North America, where it is treated by the American Ornithological Society as a subspecies of herring gull.

References

  1. BirdLife International (2018). "Larus occidentalis". IUCN Red List of Threatened Species . 2018: e.T22694337A132543621. doi: 10.2305/IUCN.UK.2018-2.RLTS.T22694337A132543621.en . Retrieved 11 November 2021.
  2. "Western Gull". U.S. National Audubon Society. Archived from the original on 24 October 2008. Retrieved 20 July 2010.
  3. 1 2 3 4 Olsen, Klaus Malling; Larsson, Hans (2004). Gulls of North America, Europe, and Asia . Princeton University Press. ISBN   978-0691119977.
  4. Harrison, Peter (1991). Seabirds: An Identification Guide. Houghton Mifflin Harcourt. ISBN   978-0-395-60291-1.
  5. Dunning Jr., John B., ed. (1992). CRC Handbook of Avian Body Masses. CRC Press. ISBN   978-0-8493-4258-5.
  6. 1 2 "Western Gull". All About Birds. Cornell Lab of Ornithology . Retrieved 20 July 2010.
  7. 1 2 Emslie, Steven D.; Messenger, Sharon L. (March 1991). "Pellet and Bone Accumulation at a Colony of Western Gulls". Journal of Vertebrate Paleontology. 11 (1): 133–136. doi:10.1080/02724634.1991.10011380. JSTOR   4523362.
  8. 1 2 Rogers, Paul (20 July 2013). "AT&T Park gulls vex San Francisco Giants". San Jose Mercury News. Retrieved 20 July 2013.
  9. 1 2 Olsen, Klaus Malling (2018). Gulls of the world : a photographic guide. Princeton, New Jersey. ISBN   978-0-691-18059-5. OCLC   1005861102.{{cite book}}: CS1 maint: location missing publisher (link)
  10. Gallo-Reynoso (2010). "Feral cats steal milk from northern Elephant Seals". Therya. 1 (3): 207–211. doi: 10.12933/therya-10-14 .
  11. Good, Thomas P.; Ellis, Julie C.; Annett, Cynthia A.; Pierotti, Raymond (2000). "Bounded Hybrid Superiority in an Avian Hybrid Zone: Effects of Mate, Diet, and Habitat Choice". Evolution. 54 (5): 1774–1783. doi: 10.1111/j.0014-3820.2000.tb00721.x . ISSN   0014-3820. PMID   11108604.

Additional sources