E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Larus glaucescens Naumann, 1840
Glaucous-Winged Gull
Family: Laridae

Species account author: Jamie Fenneman
Photo of species

© Tim Zurowski  Email the photographer   (Photo ID #11087)


Distribution of Larus glaucescens in British Columbia.
(Click on the map to view a larger version.)
Source: Distribution map provided by Jamie Fenneman for E-Fauna BC

Species Information

Breeding adult
This plumage is held between ~February/March and ~September/October. The mantle, including the back, scapulars, and most of the upperwings, is mid-grey, although the tips of the outer primaries are often slightly darker grey than the remainder of the upperwing . There is a relatively broad white trailing edge along the tertials, secondaries, and inner primaries, which breaks into smaller, discrete white tips on the outer primaries; the outer primaries also show a subterminal row of white spots that increase in size towards the outermost primary. The underside of the wings area largely white, although the undersides of the flight feathers are usually slightly greyer than the remainder of the underwing. The rump, uppertail coverts, and tail are white, as are the head, neck, and entire underparts. The iris is dark brown (rarely dusky-yellow) with a pinkish orbital ring. The yellow bill is relatively heavy, with a pronounced gonydeal angle, and sports a red spot at the gonys. The legs and feet are flesh-pink.

Non-breeding adult
This plumage is acquired in early fall (September/October) and is held throughout the winter, gradually becoming more like the breeding plumage through wear. It is similar to the breeding plumage, but the head, neck, and upper breast are extensively marked with dusky-brown smudging and barring. The bill is often paler and duller yellow than during the breeding season and often has a dusky or dark subterminal mark. The orbital ring and legs are also duller and paler pink than during the breeding season.

Third-year immature
This plumage is held between the fall of the third year and the spring of the fourth year, at which time a partial molt results in a “third-summer” plumage that last into the fall. It is overall similar to the non-breeding adult plumage, but often has heavier dusky barring and smudging on the head and neck (sometimes extending onto the underparts), more extensive black on the usually dull yellow to flesh-coloured bill (bill sometimes almost entirely black), and usually reduced white tips on the primaries. Some birds retain some brownish feathering on the upperwings, and tail typically sports a broken, irregular brownish subterminal band or, at the least, several small subterminal marks (some birds retain a largely brown tail).

Second-year immature
This plumage is held between the fall of the second year and the spring of the third year, at which time a partial molt results in a “second-summer” plumage that lasts into the fall. In relation to the first-year immature plumages, this plumage shows a variable number of mid-grey feathers coming in on the back and scapulars (and, to a lesser extent, the upperwing coverts). In addition, the rump and uppertail coverts tend to be paler and whiter, the upperwings tend to be somewhat less finely-patterned, and the bill shows a variable amount of flesh-pink at the base (ranging from a thin line along the gape to the entire inner half of the bill). Over the course of the winter and into the spring, the head, neck, and underparts become whiter, the mantle becomes more extensively grey, the upperwings become worm and paler grey-brown, and the rump and tail become whiter.

Juvenile / first-year immature
The juvenile/’first-winter’ plumage is held until the spring or early summer of the second year, at which time a partial molt produces a “first-summer” plumage that lasts until the following fall. The upperparts are wholly brown or greyish-brown, with fine paler buffy-white speckling and mottling on the back, scapulars, rump, uppertail coverts, and upperwing coverts. The tips of the tertials and secondaries have variable fine buffy-white tips, and the primaries show very thin pale fringes. The tail is wholly brown or greyish-brown, often with some fine whitish speckling near the tips of the feathers. The head, neck, and underparts are uniformly grey-brown, usually with some irregular paler mottling and very fine darker barring on the head, neck, and breast and some paler barring on the lower belly and undertail coverts. The iris is dark, the bill is uniformly blackish (often with some flesh-pink near the gape), and the legs and feet are dull flesh-pink. Over the course of the first winter and into the following spring, the plumage gradually becomes paler, especially on the upperwings (which often become almost whitish when heavily worn). Many individuals retain darker scapulars when worn, which appear as a dark grey-brown patch.

Measurements
Total Length: 55-65 cm
Mass: 946-1,180 g

Source: Sibley (2000); Howell and Dunn (2007); Hayward and Verbeek (2008)

Biology

Identification

Identification of all large gulls, especially in immature plumages, is complex and very difficult and will be covered only superficially here. The presence of large amounts of individual variation, complex and prolonged periods of immaturity, and extensive hybridization (especially in the Pacific Northwest) render gull identification among the most challenging of all bird identifications. Those wishing to study these identification challenges further are directed towards excellent publications such as Olsen and Larsson (2004) and Howell and Dunn (2007).

Glaucous-winged Gulls of all ages are relatively easily distinguished from most other large white-headed gulls in the Pacific Northwest by their mid-grey (adults) or brown (immatures) wingtips that contrast little with the colour of the upperparts. The relatively thick bill with its pronounced gonydeal angle, the long neck, and the overall bulky proportions give this species a somewhat distinctive posture, especially when perched. Adults have mid-grey upperparts that further help distinguish them from dark-mantled species such as Western Gull and Slaty-backed Gull as well as very pale-mantled species such as Herring Gull. These species, as well as Thayer’s Gull, are all further distinguished by their black or blackish (rather than grey) wingtips. Based on wingtip pattern, adults are most likely to be confused with Glaucous Gull or Iceland Gull, although both species have either white (Glaucous Gull, some Iceland Gulls) or irregularly patterned pale to dark grey wingtips (some Iceland Gulls). Iceland Gulls with grey wingtips can typically be distinguished from Glaucous-winged Gull by the more extensive white in the wingtips, paler mantle, smaller size, more slender proportions, more rounded head, much smaller bill, and (usually) pale or amber-coloured eye.

First-year immatures are very uniformly coloured brown or grey-brown, including the wingtips, and are thus relatively easy to distinguish from immatures of other large gulls such as Herring Gull and California Gull, which have blackish wingtips. First-year Glaucous Gull is often parimarily brown, but the wingtips are whitish or pale brownish-white and are paler than (rather than a similar shade to) the rest of the underparts. The sharply bicolored bill (pink at the base, black at the tip) of Glaucous Gull is also a distinctive characteristic that helps distinguish it from most Glaucous-winged Gulls (although some Glaucous-winged Gulls can have a bill pattern approaching that of Glaucous Gull). First-year Thayer’s Gull is the most likely species to be confused with first-year Glaucous-winged Gull in B.C., and given the abundance of both species in coastal B.C. this is a common identification pitfall. Thayer’s Gull tends to have wingtips that are slightly darker than the rest of the upperparts (dark brown) and, when fresh (e.g., in the fall or early winter) usually shows distinctive pale crescents at the tips of the primary feathers that, due to the darker primaries, are more contrasting than in Glaucous-winged Gull. The upperwings and upperparts of Thayer’s Gull also tend to be more prominently mottled and speckled with pale whitish or buffy-white markings, and it is a slightly smaller, more slender species with relatively shorter legs, a smaller and more domed head, and a smaller and straighter bill.

Second-year and third-year immature Glaucous-winged Gulls remain relatively easy to differentiate from other gulls due to their grey or brown wingtips (vs. blackish or whitish) as well as the increasing amount of mid-grey (rather than dark grey or pale grey) feathers on the mantle.

Source: Howell and Dunn (2007)
Vocalizations

Produces a very wide array of calls throughout the year. The most commonly-heard calls include a series of loud sounds delivered in succession (au-au-khau-khau-khau) (known as the “Long Call”), a shorter kjau, and a rapidly-repeated, guttural hoh-hoh-hoh. Also produces a high, repeated, yelping kea, a rapid ka-ka-ka alarm call, a a drawn-out ma-ah. The calls are similar to those of Western Gull but average flatter, slower-paced, lower-pitched, and more hollow-sounding.

Source: Sibley (2000); Howell and Jaramillo (2006); Hayward and Verbeek (2008)

Breeding Ecology

Courtship

This species is monogamous, with pairs forming on the breeding grounds in the late winter or early spring (February to April) and remaining together throughout the breeding season. Courtship includes a wide variety of displays such as head tossing (in which the head is jerked back), allopreening (in which one individual preens the feathers of its mate’s head), and courtship feeding. In one courtship display, known as the “Mew Display”, the displaying bird holds the body horizontal or slightly oblique, arches the neck, points the head downwards, and producesa mewing call; this display is also associated with non-courtship functions (territoriality, etc.).

Nest
The nest is constructed in late April and May, although some birds may begin the first nest scrapes as early as March. The nest is situated on the ground or other flat structure (pier, building roof, etc.); nests are rarely placed in large tree. This species is generally colonial, although isolated pairs regularly occur as well, and colonies are regularly associated with other colonial seabirds such as cormorants and alcids. The nest is typically placed in a shallow scrape or on a low mound and is enclosed by a bulky ring of loose grass, moss, dead twigs, string, garbage, bones, seaweed, feathers, and other debris. Nests average 38-39 cm in diameter (21-22 cm inside diameter) and 10-11 cm in depth.

Eggs
A single clutch of (2) 3 (4) eggs is laid between late April and late July, with most clutches laid in May or June. The eggs are incubated by both sexes for 26-29 days before hatching. The smooth or slightly granular, non-glossy eggs range in colour from pale greenish or olive-green to greyish-olive or buff and are variably marked with dark brown, grey, and olive scrawls and blotches. This species does not lay a second clutch, but replacement clutches are laid if the first clutch is lost. Eggs have been recorded in B.C. between late April and mid-August.

Young
The young are semi-altricial upon hatching, with a complete covering of down. The down is buffy, with black spots on the head and throat, blackish-grey patches on the back and flanks, and an area of blackish-based and light-tipped feathers across the breast; the upper surface of the wings and occasionally the belly also have some dark spotting. The legs and feet are dull flesh-coloured at hatching but quickly turn blackish and the bill is black with a dusky-pink outer third. The young are able to leave the nest almost immediately after hatching, and remain in the vicinity of the nest for the first few days after hatching. The chicks gradually range farther from the nest, and are tended by both adults throughout the fledgling stage. The fledglings are capable of flight at 35-54 days of age, at which point they leave the colony and are fully independent shortly thereafter. Dependent fledglings have been observed in B.C. between early June and mid-September.

Source: Campbell et al. (1990b); Baicich and Harrison (1997); Hayward and Verbeek (2008)
Foraging Ecology

Like many large gulls, the Glaucous-winged Gull consumes an enormous array of food items throughout the year and is considered an opportunistic and omnivorous species. Major food items include fish, marine invertebrates, carrion, and (in areas near communities) garbage. In the marine environment, this species can be found along virtually any coastline or estuary in search of fish (both dead and alive) and marine invertebrates such as crabs, shellfish, sea stars, marine worms, etc. It commonly carries shellfish and crabs into the air and drops them onto hard shoreline rocks to break the shells, while other large invertebrates (such as sea stars) are often swallowed whole. It also pursues small surface-feeding fish, and large aggregations of gulls often swarm schools of fish and attempt to capture individuals by dipping their heads under the water or engaging in shallow dives from a few metres in the air. Particularly large concentrations of Glaucous-winged Gulls are associated with spawning events of herring and salmon, where they prey on both live and dead fish as well as the abundance of eggs that they produce.

Where it ocurs near cities and towns, this species feeds extensively on garbage, both at landfills and throughout urban areas. It also consumes carrion, and will wait near feeding carnivores such as bears and eagles in order to steal scraps as they are left unguarded. The eggs and nestlings of a wide variety of birds, especially colonial marine species (cormorants, other gulls, etc.), are also a common food item, and it regularly engages in kleptoparasitism or piracy (stealing food items from other birds).

Source: Hayward and Verbeek (2008)

Habitat


The Glaucous-winged Gull is found in all nearshore marine and estuarine habitats along the coast of B.C., and regularly ranges into low elevation freshwater habitats such as rivers, streams, and lakes (especially during salmon spawning events). It often concentrates in sheltered coastal habitats such as harbours, bays, lagoons, but also ranges widely into offshore and pelagic environments, especially outside of the breeding season. It regularly occurs in a variety of terrestrial habitats as well, including agricultural fields (both dry and flooded), landfills, urban and suburban environments, and tends to avoid only areas of extensive forests and higher elevations. Nesting birds occur primarily on small, rocky, usually treeless offshore islets, although some pairs may nest on structures such as buildings, pilings, jetties, log booms, and navigation buoys or on coastal headlands and cliffs. In the southern interior, it is usually found in association with mixed-species gull flocks at landfills, river bars, large lakes, and river mouths.

Source: Campbell et al. (1990b)

Distribution

Global Range

This species breeds in coastal areas of the North Pacific, including along the west coast of North America (from western Alaska south to Oregon) as well as on the Kamchatka Peninsula, the Commander Islands (Russia), and along the Russian coast of the Bering Sea. It ranges farther south in winter, regularly occurring as far as northwestern Mexico and Japan. It is a casual (but increasing) vagrant throughout much of North America away from the Pacific coast.
BC Distribution

Breeding
Common and widespread breeder along the entire coast of the province, including all offshore islands. It is also a local breeder in the Okanagan Valley of the south-central interior, where it breeds at only a single location in Okanagan Lake (Jim Grant [Whisky] Island) and is uncommonly found throughout much of Okanagan Lake during the summer months.

Winter
Common to abundant during the winter along the entire coast, both in nearshore marine environments as well as on lakes and rivers at low elevations; uncommon to fairly common in offshore waters far off the coast of B.C. throughout the winter. In the south-central interior, it is ucommon throughout the Okanagan Valley and rare in the Thompson, Nicola, and southern Fraser Basins. Casual in winter in the West Kootenays.

Migration and Vagrancy
Populations along the coast are largely resident, although they are augmented in winter by migrants from more northerly-breeding populations. In the south-central interior, populations occur year-round in the Okanagan Valley, although numbers increase in late fall (late October or early November) and remain somewhat higher into February. Elsewhere in the south-central interior (e.g., Thompson and Nicola Basins), small numbers appear in September (very rarely in August) and typically remain into late December or January, with a very few individuals occasionally remaining through the winter and into the early spring (late March or April).

Casual spring and summer vagrant throughout the southern interior away from the Okanagan Valley. Casual vagrant from spring through fall in the central and northern interior.

Source: Campbell et al. (1990b); Kenyon et al. (2009)

Conservation

Population and Conservation Status

This species is abundant in coastal areas of B.C., and is usually the most common species of gull throughout the year at most coastal localities. Populations on the coast of B.C. have increased by at least 300% over the past 70 years, likely in response to the abundance of food sources provided by landfills, fish processing plants, and urban environments. It has also been increasing as a winter visitor in the south-central interior, especially in the Okanagan Valley, where it has also recently become established as a breeding species. The Glaucous-winged Gull is not recognized as a species of concern by either provincial (B.C. CDC [Conservation Data Centre]) or federal (COSEWIC [Committee on the Status of Endangered Wildlife in Canada]) authorities.

Source: Campbell et al. (1990b)

Taxonomy


This species is monotypic, with no recognized subspecies, although northern (Alaskan) breeders average paler than birds breeding along the coast of British Columbia.

This species hybridizes extensively with other large white-headed gulls where their ranges overlap. This is most pronounced along the coasts of Washington and Oregon (and locally in extreme southwestern B.C.), where the majority of individuals represent hybrids between Glaucous-winged Gull and Western Gull. These birds, which are sometimes known as “Olympic” Gull or “Puget Sound” Gull, disperse widely along the coast of B.C., especially outside of the breeding season, and can sometimes outnumber pure Glaucous-winged Gulls in areas such as the Strait of Georgia, Strait of Juan de Fuca, and along the west coast of Vancouver Island. Similarly, relatively few “Western” Gulls observed on the coast of B.C. represent genetically “pure” individuals, with most birds showing some indications of hybridization with Glaucous-winged Gull (e.g., more extensive head markings in winter, grey underside of the primaries, paler mantle colour, etc.).

This species also hybridizes widely with Herring Gull in south coastal Alaska (and occasionally in the Okanagan Valley of south-central B.C.), and representatives of this hybrid are widespread and relatively frequent along the coast of B.C. during the winter months. Rarer hybrid combinations include Glaucous x Glaucous-winged Gull (hybridizing on the Bering Sea coast of Alaska), which is rare in winter and migration in coastal B.C., and Slaty-backed x Glaucous-winged Gull (hybridizing on the Kamchatka Peninsula and Commander Islands of Russia), which has not been reported in B.C., but may be expected as the frequency of Slaty-backed Gull in the Pacific Northwest and Alaska continues to increase.

Source: Howell and Dunn (2007); Hayward and Verbeek (2008)

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS4YellowNot Listed
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-04-12 5:28:07 PM]
Disclaimer: The information contained in an E-Fauna BC atlas pages is derived from expert sources as cited (with permission) in each section. This information is scientifically based.  E-Fauna BC also acts as a portal to other sites via deep links.  As always, users should refer to the original sources for complete information.  E-Fauna BC is not responsible for the accuracy or completeness of the original information.


© E-Fauna BC 2021: An initiative of the Spatial Data Lab, Department of Geography, UBC