Bird of the Month: Western Gull
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
The Western Gull is a large, white-headed gull with a dark gray mantle, pink legs, and a large, bulbous yellow bill with a red spot toward the tip. In winter Western Gulls move into Puget Sound and can more readily be seen by local birders.
COMMON ALONG THE PACIFIC COAST
Western Gulls are the only gull that breeds along the Pacific coast from Washington to Baja California. Once young birds leave the colony, they stay within the large breeding area and travel inland only short distances staying close to waterways. They are common on beaches, waterfront areas, around human structures, and at sea.
Their natural diet consists of a wide variety of sea animals including fish, crabs, squid, mussels, and clams to name a few. They will also eat the eggs, young, and sometimes adults of other seabirds. Those gulls around sea lion colonies will scavenge on dead pups and afterbirth (Kaufman). When sources of good food are scarce, they will feed at landfills (Pierotti and Annett).
The Western Gull is one of the many gulls in the genus Larus, from the Greek laros, for a ravenous seabird. There are 32 gulls in this genus worldwide; 17 are North American gulls. Occidentalis is Latin for pertaining to the west in reference to this gull’s natural territory in western North America. “Gull” is from the Celtic gullan or gwylan, which names for this type of bird (Holloway).
COLONIAL NESTER
Like many gull species, the Western Gull nests in large colonies. The nest is a shallow depression lined with grass, and may be constructed on a cliff, under an overhang, or on the ground. Usually, three eggs are deposited. Incubation lasts for about a month and juveniles may leave the nest when two days old and hide in nearby vegetation. The young will be capable of flight in another 6-8 weeks and leave the colony several weeks after that (Kaufman).
Most Western Gulls nest south of Washington, however, a colony of about 4,000 pairs breeds on or near Destruction Island, which is located about three miles off the shore of the Olympic Peninsula near Hoh, WA. Despite the fact that the Western is one of the largest gulls in the west and the only one to breed along the Pacific coast, it has a relatively small population of 40,000 pairs (Pierotti and Annett).
Western Gull
Scientific Name: Larus occidentalis
Length: 25”
Wingspan: 58”
Weight: 2.2 LB (1,000 g)
AOU Alpha Code: WEGU
CONSERVATION AND MANAGEMENT
The only management plans for Western Gulls have been based on the goal of limiting their population and predation on Leach’s and Ashy Storm-Petrels, and Cassin’s Auklets. However, caution has been advised when attempting to control the numbers of Western Gulls, because this gull has a much smaller population by comparison to the seabirds and its impact on Leach’s Storm-Petrel and Cassin’s Auklet is relatively limited. Some control may be needed to protect Ashy’s Storm-Petrel (Pierotti and Annett).
The National Park Service has corrected its management programs and Western Gulls have recovered from now-discontinued control programs and are nesting again on Alcatraz Island in San Francisco Bay and Southeast Farallon Island (Pierotti and Annett). A balanced approach to management will help both the seabirds and the Western Gulls.
A NOTE ON INTERBREEDING
Glaucous-winged Gulls nest in the same area with Western Gulls and will interbreed with them producing the Western x Glaucous-winged Gull (hybrid), known locally as the “Olympic Gull.” These hybrid gulls are abundant in the intergradation zone and in some areas may make up 75% of the gulls (Howell and Dunn). The Western x Glaucous-winged Gull (hybrid) floods into the Puget Sound area in winter. These hybrids have a wide range of plumage characteristics combining some structural and plumage characteristics of both the Western Gull and the Glaucous-winged Gull.
Extensive hybridization between these two species presents a risk to the Western Gull population. However, some ornithologists consider the two to be conspecific, i.e., the same species of gull (Howell and Dunn). If this turns out to be true, then interbreeding may not matter.
Photo credit Mick Thompson. References available upon request from amccormick@eastsideaudubon.org.