Western Gull – Facts | Description | Hybridization

western gull

The western gull, scientific name Larus occidentalis is a large white-headed gull that lives on the west coast of North America. It was earlier thought-about conspecific with the yellow-footed gull (Larus livens) of the Gulf of California.

The western gull ranges from British Columbia, Canada to Baja California, Mexico. This article will give an overview of Facts, Predators, vs California gull, vs herring gull, in-flight, flying and adaptations and sounds.


The western gull is a big gull that may measure 55 to 68 cm (22 to 27 in) in complete size, spans 130 to 144 cm (51 to 57 in) throughout the wings, and weighs 800 to 1,400 g (1.eight to three.1 lb).

The common mass amongst a survey of 48 gulls of the species was 1,011 g (2.229 lb).

Amongst normal measurements, the wing chord is 38 to 44.eight cm (15.zero to 17.6 in), the invoice is 4.7 to six.2 cm (1.9 to 2.Four in) and the tarsus is 5.eight to 7.5 cm (2.three to three.zero in).

The western gull has a white head and physique, and grey wings. It has a yellow invoice with a purple subterminal spot (that is the small spot close to the top of the invoice that chicks peck with the intention to stimulate feeding).

It intently resembles the Slaty-backed gull (Larus schistisagus). Within the north of its vary it kinds a hybrid zone with its shut relative the glaucous-winged gull (Larus glaucescens).

Western gulls take roughly 4 years to succeed in their full plumage,[6] their layer of feathers, and the patterns and colors on the feathers.

The western gull sometimes lives about 15 years, however, it can dwell as much as 25 years.

The biggest western gull colony is on the Farallon Islands, situated about 26 mi (40 km) west of San Francisco, California; an estimated 30,000 gulls dwell within the San Francisco Bay space. Western gulls additionally dwell within the Oregon Coast.

Distribution and habitat

The western gull is a year-round resident in California, Oregon, Baja California, and southern Washington.

It’s migratory, transferring to northern Washington, British Columbia, and Baja California Sur to spend the nonbreeding season.


The western gull hardly ever ventures greater than roughly 100 miles inland, nearly by no means very removed from the ocean; it’s nearly a completely marine gull.

It nests on offshore islands and rocks alongside the coast, and on islands inside estuaries. A colony additionally exists on Anacapa Island and Alcatraz Island in San Francisco Bay.

Within the colonies, long-run pairs aggressively defend territories whose borders could shift barely from 12 months to 12 months, however, they are maintained for the lifetime of the male.


Western gulls feed in pelagic environments and in intertidal environments. At sea, they take fish and invertebrates like krill, squid, and jellyfish.

They’re unable to dive and feed completely on the floor of the water. On land, they feed on the seal and sea lion carcasses and roadkill, in addition to cockles, starfish, limpets, and snails within the intertidal zone.

In addition, they feed on human meals refuse, in human-altered habitats together with landfills, and take meals given to them, or stolen from individuals at marinas, seashores, and parks.

Western gulls are recognized to be predatory, killing and consuming the younger of different birds, particularly ducklings, and even the adults of some smaller hen species.

Western gulls, together with one who lived at Oakland’s Lake Merritt are recognized for killing and consuming pigeons (rock doves).

They may even snatch fish from a cormorant’s or pelican’s mouth earlier than it’s swallowed.


A nest of vegetation is constructed contained in the dad or mum’s territory and three eggs are laid. These eggs are incubated for a month.

The chicks, as soon as hatched, stay contained in the territory till they’ve fledged. Chicks straying into the territory of one other gull are liable to be killed by that territory’s pair.

Chick mortality is excessive, with on common one chick surviving to fledge. Now and again, deserted chicks can be adopted by different gulls.


In Washington state, the western gull hybridizes continuously with the glaucous-winged gull, and will intently resemble a Thayer’s gull.

The hybrids have a flatter and bigger head and a thicker invoice with a pronounced angle on the decrease a part of the invoice, which distinguishes it from the smaller Thayer’s gull.

One in every of our extra widespread gulls. Definitely the most typical at ports, docks, and round seaside human exercise.

Adults in breeding plumage, just like the hen pictured above, are usually not laborious to determine, however, Western gulls take 4 years to achieve full grownup plumage, and the juvenile and intermediate phases could be very complicated.

Gulls are excellent at making individuals really feel ignorant. Please be happy to level out errors or omissions. If unsure, test the books.

The standard grownup in breeding plumage is characterized by a heavy college bus-yellow invoice with a pronounced widening towards the tip (the gonys) normally marked by a purple spot.

In contrast to many different widespread gulls in Sonoma County, the top and breast stay clear white within the winter (most gulls turn into streaked with varied shades of brownish-gray within the winter).

Observe the pink legs and darkish grey again (the mantle)–although color could be tough to evaluate in several lights and there’s an excessive amount of color variation from hen to hen and amongst completely different populations (northern California Western Gulls are usually lighter gray).

Inbreeding plumage, Western Gull has a brilliant yellow-orange eye-ring. The attention itself is pretty darkish (see photograph under).

The primaries are tipped with black however have small, distinct, white “mirrors.” Juvenile birds are principally brown.

See the standard information books and Gulls of the Americas for the development of plumage modifications by way of the 4 years to maturity. The one gull that breeds in Sonoma County. Usually nests off Bodega Head.

Maybe almost definitely to be confused with Herring Gull, however, Herring Gull has a straighter invoice profile (much less of the bump on the tip), the invoice is a clearer yellow (much less orange), the mantle will are usually paler, the “mirrors” within the primaries can be greater, and Herring Gull has a pale eye (with a pale yellow eye-ring in breeding plumage), though at a distance or in flight, particulars of the attention are usually not very helpful and eye color is considerably variable. In winter, Herring Gull could have a streaked head.

Western gulls and people

The western gull is presently not thought-about threatened. Nonetheless, they’ve, for a gull, a restricted vary.

Numbers had been drastically diminished within the 19th century by the taking of seabird eggs for the rising metropolis of San Francisco.

Western gull colonies additionally suffered from disturbance the place they had been becoming lighthouse stations, or, within the case of Alcatraz, a jail.

Western gulls are very aggressive when defending their territories and consequently had been persecuted by some as a menace.

The automation of lighthouses and the closing of Alcatraz Jail allowed the species to reclaim components of its vary. They’re presently susceptible to climatic occasions like El Niño occasions and oil spills.

Western gulls have turn into a critical nuisance to the San Francisco Giants baseball workforce. Hundreds of gulls fly over AT&T Park in San Francisco throughout the late innings of video games.

They swarm the sector, defecate on followers, and after video games eat leftovers of stadium meals within the seats; how the birds know when video games are about to finish is unknown.

The gulls left whereas a red-tailed hawk visited the park in late 2011, however, they returned after the hawk disappeared.

Federal regulation prohibits capturing the birds, and hiring a falconer would price the Giants $8000 a sport.

This species has a really massive vary and therefore doesn’t strategy the thresholds for Susceptible underneath the vary dimension criterion (Extent of Incidence <20,000 km2 mixed with a declining or fluctuating very dimension, habitat extent/high quality, or inhabitants dimension and a small variety of places or extreme fragmentation).

The inhabitants’ pattern seems to be growing, and therefore the species doesn’t strategy the thresholds for Susceptible underneath the inhabitant’s pattern criterion (>30% decline over ten years or three generations).

The inhabitants’ dimension may be very massive, and therefore doesn’t strategy the thresholds for Susceptible underneath the inhabitants’ dimension criterion (<10,000 mature people with an unbroken decline estimated to be >10% in ten years or three generations, or with a specified inhabitants construction). For these causes, the species is evaluated as Least Concern.

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