Illustration: California gull

Illustration by Thomas R. Schultz

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Map: California gull range

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A midsize gull of the Western interior, the California is closely tied to saline lakes. Polytypic. Length 21" (53 cm); wingspan 54" (137 cm).

Identification A medium- to large-size, long-legged, long-billed, and long, narrow-winged 4-year gull. Bill characterized by being nicely parallel sided, lacking an expansion at the gonydeal angle. Summer adult: a dark gray mantled gull, darker than the ring-billed gull. White head, neck, underparts, and tail. Bright yellow bill with a red gonys spot and a black subterminal band. During breeding period the black bill band is reduced in size; on some birds it may be nearly absent. Eye dark, with bright red orbital ring, carmine gape. Greenish yellow legs. The wing pattern is distinctive: this gull shows extensive black on the primaries, particularly so on P8 and P7, giving the black wing tip a nearly square-cut shape. The mirrors on P9 and P10 are large. Winter adult: simi­lar to breeding adult, but head and neck streaked brown, concentrated on back of the neck, nape, and lower neck sides; often with a dark postocular streak. Throat and front of neck are unstreaked. Juvenile: usually dark, grayish brown, although some cinnamon brown, and often whitish on the center of the breast and belly. Bill all dark. The wings lack paler inner primaries, and they show dark-based coverts. The tail is largely dark, and the legs are pink. First-year: like the juvenile, but bill bicolored with pink base and black tip. Juvenal scapulars replaced by variable patterned feathers, but tend to show a solid gray-brown center and shaft streak and a large buffy gray tip with a narrow blackish terminal fringe. Summer birds with whiter head and worn and faded wings, contrasting with newer mantle. Second-year: dark gray mantle; browner wings with marbled pattern on coverts and tertials, often some gray inner median coverts present. White head, neck, and underparts with streaks concentrated on ear coverts, nape, and particularly the breast sides. Bicolored bill, with grayish to gray-green base; legs similarly greenish gray. Wing pattern at this age shows blackish outer primaries clearly contrasting with paler gray inner primaries; dark secondary bar. Tail remains blackish, but now contrasts with white rump and uppertail coverts. In second-summer, head and body much more whitish; may obtain more adultlike soft-part colors. Third-year: like adult, but retains dark on greater primary coverts and tail. White mirrors on primaries not as well developed.

Geographic Variation Nominate subspecies breeds east to Colorado, Utah, and Idaho. Subspecies albertaensis farther east and north in Northwest Territories, Alberta, Saskatchewan, Manitoba, North and South Dakota; intermediates in Montana. It is larger, larger-billed, and paler on mantle than californicus, and it has a tendency to show less black on the primaries and larger mirrors, with that of P10 often with entirely white tip.

Similar Species Distinguished from the adult herring gull by darker mantle, dark eyes, greenish legs, and black and red on bill tip. Second-year birds similar, but note the California’s darker mantle, dark eyes, grayish bill base and legs, as well as structural differences. First-year Californias can be told from first-year lesser black-backeds by their more extensively dark tail, bicolored bill, and blotchy, pale tipped scapulars.

Voice Long call: a series of kyow notes; the first 2 are longer and more drawn out. Call is higher pitched than corresponding call of the herring gull.

Status and Distribution Abundant. Breeding: colonies on flat islands, some on saline lakes. Migration: moves to coast after breeding. In summer and early fall, shows a generally northward movement. Southward movements begin in fall and winter, reaching southernmost winter range in midwinter, before moving north again. Interior birds, albertaensis, appear to move farther south than californicus and return slightly later in spring. Winter: shifts to Pacific coast and interior near coast during winter. Vagrant: casual throughout interior to East Coast, appears to be increasingly regular as a vagrant to east.

Population Estimated between 500,000 and 1 million individuals. Population in United States estimated to have doubled since 1930. Increases ongoing: for example, in San Francisco Bay, California breeders increased from 400 to over 21,000 in last 20 years.

—From the National Geographic book Complete Birds of North America, 2006

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