California Gull californicus

(last update: 22-12-2016 )

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Alex Abela
John Cant
Mars Muusse

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adult: August

CALIFORNIA GULL Larus californicus Description in "Gulls of North America, Europe, and Asia", by Klaus Malling Olsen & Hans Larsson, Princeton University Press.

This is a copy of the chapter on California Gull, written by Klaus Malling Olsen. "I" in the text refer to the author. If you find any errors, please let me know at marsmuusse at gmail dot com.

CALIFORNIA GULL Larus californicus
(Lawrence, 1854, Stockton, California)

PART 1: IDENTIFICATION (below)
PART 2: VOICE & DESCRIPTION
PART 3: GEOGRAPHICAL VARIATION & MEASUREMENTS

IDENTIFICATION

Length 45-51cm, wingspan 122-140cm. California Gull is between Herring and Ring-billed Gull in size. It resembles Ring-billed but has a larger, slimmer and longer bill, smaller head, deeper breast and belly, more attenuated body and wings, shorter legs and dark eyes. The long wings are often lowered when settled. In flight it is slender with a deep breast, flat or slightly concave belly and narrow wings. California Gull takes four years to develop fully adult plumage as in larger gulls, making precise ageing difficult apart from first-year and adult. Two subspecies discernible (Jehl 1987a & b, King 2001), both rather similar; separation of albertaensis discussed under Geographical Variation.

Adult has dark grey upperparts with prominent white scapular and tertial crescents and trailing edge to inner wing. The clean-cut black wing-tip appears as a triangle with white mirrors on P9-10; on the otherwise white underwing the darker secondaries create a rectangle. Eyes are dark, surrounded by a red orbital ring. Bill yellow with red gonys-spot, dark markings and paler tip, often appearing four-coloured - a pattern unique in West Coast gulls. Often shows a long, reddish gape-line. Legs grey to yellow. In many ways resembles adult Armenian and Caspian Gull taxon barabensis.

In summer head is white and bill greenish-yellow with dark markings normally restricted to lower mandible. Orbital ring red. Legs yellow, often with greenish tinge.

In winter head has dark patterning, mainly as hindneck-streaks, creating a darker necklace which may reach breast-sides. Bill and legs duller and more variable than in summer, bill with broader dark subterminal bar and often ivory tip. Orbital ring sometimes dark.
May be confused with Ring-billed, which is normally slightly smaller with paler upperparts, a generally larger and bulkier head, shorter, blunter-tipped bill with a more complete black bill-ring, pale eyes and slightly longer, yellow legs. In settled birds, white crescent and tertial edges weaker and wings shorter with more evenly spaced white primary tips; in California, spacing between white primary tips more uneven, broadest on inner visible primary tips. In winter, Ring-billed has coarser dark head-markings, covering most of head and reaching breast to upper flanks.
Compared to American Herring, California Gull is smaller with rounder, smaller head, narrower bill and larger dark eyes situated more to the front of the head.  The hindparts are narrower, wings longer and legs shorter. In most plumages it is darker than American Herring, often with grey legs showing a blue or greenish tinge not present in American Herring.

Juvenile has a dark brown head and underparts with a paler forehead, central belly and undertail-coverts, the latter brown-barred or mottled. The fresh juvenile plumage is often strongly cinnamon or buffish-tinged. The upperwing is dark with slightly paler coverts and 1-2 pale bars created by dark bases to the greater and median coverts; there is rarely a slight pale window on the inner primaries. The upperparts are dark brown with indistinct mottled feather-edges. The greater coverts may be almost uniform dark, forming a dark midwing-panel, but some birds have entirely barred or mottled greater coverts, together with solid dark-centred tertials generally darker than rest of upperparts. Tail dark against the heavily barred rump. Underwing dark with slightly paler flight feathers. Bill blackish and legs fleshy.
In darkest birds, the dark overall plumage may approach first-year Heermann’s, but lower belly and undertail-coverts are paler, bill often darker and legs fleshy, not dark.

First-winter similar to juvenile, but head generally paler with clearer dark hindneck spots and more conspicuous pale forehead. Mantle and scapulars grey to greyish-brown with variable dark streaks, subterminal bars or narrow spots. Bill develops pale base from Oct, and becomes fleshy with clear-cut black tip in winter, the pale base merging into the pale face. Legs fleshy to greenish-grey. Combination of bill, rather uniform head with pale blaze (and sometimes neck-sides), weakly mottled underbody, dark-streaked grey mantle, greenish-tinged legs and small size separates the plumage from other gulls. From late winter, pale mid-wing-panel on upperwing is developed through wear of median coverts, and the greater covert bar is more conspicuous.

In first-summer, the head and underbody are whitish and retained juvenile feathers strongly faded.

Second-winter has white head and underbody with dark-streaked necklace and breast-sides, which may be barred. Saddle grey, in contrast to wing, which is similar to first-year, apart from darker greater coverts with fainter pale mottling (often restricted to innermost), creating brown carpal bar on inner wing. Parts of coverts renewed to adult type. Tertials with triangular dark centres and white edges. Compared to first-years, flight feathers darker with more conspicuous pale window on inner primaries, broader rounded white tips and rarely white mirror on P10. Rump white with barely any dark pattern, contrasting strongly with dark, white-edged tail. Underwing pale with dark tips to axillaries and coverts, creating dark rows. Bill duller than in adult with black subterminal bar or tip. Legs pale grey with bluish, green or fleshy tinge.

Second-summer similar to second-winter, but with more adult-type inner wing-coverts; often contrasting well with retained second-winter coverts. Bill yellowish-tinged.

Third-winter similar to adult, but with most of lesser and greater coverts of second-year type, dark-centred primary coverts and broken, blackish tail-bar. Wing-tip duller brownish-black with white mirror on P10 only; white primary tips narrower or lacking. May show a few dark-centred greater coverts and secondaries (rarely all) and black bill-tip.

Third-summer as adult, but before moult with age-characters of third-winter.

Fourth-winter as adult, but black on wing-tip duller with white mirror on P10 only, black shaft-streaks on primary coverts, traces of dark (often greyish) on tail, generally less yellow tinge to legs and blacker, more complete black ring around bill-tip.

CONTINUE PART 2: VOICE & DESCRIPTION
PART 3: GEOGRAPHICAL VARIATION & MEASUREMENTS