Note the very dark back and wings, contrasting with the snowy underparts. Feet dull pinkish. The northern race, occidentalis
(central California to Washington) has a paler mantle, which, however, is still noticeably darker than that of the California Gull. The southern race, wymani, is blacker backed. See the presentation of plumage sequences.
iNote: There is some hybridization with the Glaucous-winged Gull where its breeding range overlaps with the Westerns.
Coastal waters, estuaries, beaches, city waterfronts.
Mostly along immediate coast, but regularly found well out at sea, especially between coast and nesting islands. Visits garbage dumps, ponds, and flat open areas (such as parking lots) within a few miles of coast, but almost never found farther inland. N
ests on islands and locally on mainland cliffs.
Fish and other marine life, eggs, carrion, refuse.
Feeds on a wide variety of aquatic life, including fish, crabs, squid, clams, sea urchins. Eats eggs and young (and sometimes adults) of other birds. Around sea lion colonies, scavenges dead pups and afterbirth. Also eats other carrion, and scavenges in
dumps and around docks for refuse.
Behavior: Forages while walking or swimming, or may plunge into water from flight. May drop hard-shelled clams and crabs onto rocks while in flight to break them open.
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence 30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern. [conservation status from birdlife.org]
First breeds at 4 years or older. Nests in colonies. Courtship displays include tossing head up and back repeatedly; courtship feeding of female by male.
Nest: Site is on ground or on cliff ledge, sometimes on boat or building. Nest (probably built by both sexes) is shallow depression, usually with lining of grass, other plants.
Clutch Usually 3, sometimes 1-5, rarely 6 (clutches of more than 3 eggs result from two females laying in same nest). Eggs buff to olive or gray, blotched with brown. Incubation by both parents (female may do more), 25
-29 days. In very hot weather, adults may fly to water and soak belly feathers to cool eggs.
Young: Fed by both parents. May leave nest when a few days old and hide nearby. Able to fly at about 6-7 weeks. Young depart from some colonies at about 10 weeks, becoming independent then.
coast from Baja California to northwestern Washington. Migration:
Present all year throughout its breeding range, but banding records show that individuals wander widely within this range. Some move north into British Columbia and south to southern Baja, especially in winter. Almost never found inland.
- spanwidth min.: 120 cm
- spanwidth max.: 144 cm
- size min.: 56 cm
- size max.: 66 cm
- incubation min.: 25 days
- incubation max.: 29 days
- fledging min.: 42 days
- fledging max.: 49 days
- broods 1
- eggs min.: 1
- eggs max.: 3
- Conservation Status
- Larus occidentalis wymani
- c California (USA) to Baja California (Mexico)
- Larus occidentalis occidentalis
- sw British Columbia, w USA to c California
- Larus occidentalis
- NA w coast