California Gull californicus

(last update: 22-12-2016 )

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John Cant
Mars Muusse

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adult: September

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

VOICE

Higher and quicker, more squeaky and hoarse than in American Herring Gull. A short, deep gaaal similar to call of Great Black-backed Gull. Long-call rapid, high and wheezy (Sibley 2000).

MOULT (ssp. californicus)

Adult moult to winter plumage is complete mid-Jun - Nov. P1-2 mid-June, P4-6 late Jul-Aug, P10 late Oct-late Nov. Head Aug.

Moult to summer plumage partial Feb-Mar, including head and body. By mid-Feb >95 % still have dark head-markings; last to be lost are hindneck streaks. By Apr, most have summer head, but often still a few dark streaks on ear-coverts and hindneck.

Juvenile moult to first-winter partial Aug/Sep-Feb, including head and body, often restricted to mantle/scapulars. Moult slow with much individual variation. Mantle/scapulars generally Oct-Dec, but often with juvenile feathers admixed into Mar.

Moult into first-summer but complete into second-winter late Apr-Oct, starting with mantle/scapulars and P1, followed by head, body and coverts (starting late Apr-early Jun). P1 late Apr-early May, P4-5 mid-Jun-Jul, P7-8 Aug, P9-10 Sep-Oct. Some populations (probably albertaensis) have later primary moult, reaching P4-6 Sep-early Oct and P9-10 late Nov.

Moult to second-summer partial Mar-May, including head and sometimes parts of underbody; could be regarded as start of complete moult into third-winter, which starts Mar-Apr with mantle and scapulars (>50% renewed May-Jun) and some wing-coverts. P1 usually from late Apr, but sometimes not before mid-Jun. P9-10 (early)mid-Sep - mid-Oct.

DESCRIPTION (californicus)

Adult Mantle, back, scapulars, tertials and upperwing-coverts dark blue-grey (Kodak Grey Scale 6-7.5), scapulars and tertials with prominent white edges. Secondaries with white tips, creating striking white trailing edge to inner wing. Primaries with grey bases and black outer parts/ tips. P10 black with 32-45mm white mirror and 1-6 mm black subterminal bar near tip (often as isolated black spots; lacking in 9%, creating complete white tip of max. 55mm). P9 black with 5-25mm white mirror, sometimes oval-shaped or divided by black shaft-streak; a small proportion lack white mirror (King 2001). Black on outer web of P9-10 reaches primary coverts. P8 black (120-140mm on outer web, 70-100mm on inner); division between grey and black sometimes dark-mottled. Black on P8 reaches primary coverts in 56%; if base grey (max. 20mm), division between grey and black diffuse. P7 grey with 80-90mm black tip on outer and 40-60mm on inner web, running along shaft and reaching primary coverts in 84-95% (King 2001). P6 with 50-70mm black on outer web, 25-50mm on inner. P6-7 often with narrow white crescent-shaped division between grey and black. P5 with 10-355mm black subterminal bars near tip; sometimes restricted to black spot on outer web; may show black U-markings on both webs. Have narrow white tongues between black and grey, sometimes weak. P4 on 15-20% with black markings. Primaries with 8-15mm white tips, broadest on innermost. Tail, rump, under-body, axillaries and underwing-coverts white; from below, grey-centred secondaries create grey rectangle against white coverts. Bill yellow with red gonys-spot, black subterminal markings and often ivory tip. Gape red. Iris greyish-olive to dark brown, in birds with extensive amount of dark spotting appearing blackish; 10% with faint mottling, enough to create dull yellow eyes. Orbital ring red, yellow or violet-brown (Johnston 1956). Legs yellow, often with a greenish tinge; see under adult winter for variation.

Adult summer (Mar-Sep) Head white. Orbital ring red. Bill yellow with a red gonys-spot, often merging with narrow blackish subterminal bar (sometimes incomplete and restricted to lower mandible; rarely lacking); tip paler ivory to yellow. Legs yellow.

Adult winter (Oct-Apr) Head white with variable, often extensive brown streaks or spots, especially on hindneck, where they form a necklace in 98% of birds checked in California/Mexico late Jan-Feb, in 38% even with streaking on ear-coverts, and in 10% reaching crown. A minority show an evenly streaked head, and may appear hooded; <1% white-headed by early Feb (pers. obs.). Hindneck-streaks may reach breast-sides. Cheek, throat and foreneck sometimes with indistinct dark spots. Orbital ring dull red to black. Bill four-coloured: paler yellow than in summer plumage, with more complete black subterminal bar (max. 8mm), merging with reddish-orange to red gonys-spot. Tip ivory. Leg colour variable: from 207 adults mid-Jan - mid-Feb legs grey (37%), yellowish-grey (31%), greenish-yellow (18%), greyish-yellow (5%), bluish-yellow (4%) and yellow (3%); in <1% bright yellow or fleshy; seemingly larger percentage of yellow among N Mexican birds may be food-related (pers. obs., California and N Mexico).

Juvenile (fledging-Sep/ Nov) Head and underbody greyish-brown, cinnamon, yellowish-buff, pale tan or dark brown, mottled. Warm coloration soon lost by wear. Forehead, lores and chin paler, often as pale blaze. Crown, ear-coverts, eye-mask and hindneck darker. Lower belly paler, often merging into dark-barred white undertail-coverts. Mantle and scapulars greyish-brown with sandy fringes, sometimes as dots along edges. Tertials pale brown to blackish-brown with pale edges, broadest on tips and sometimes mottled along edges; may show darker subterminal markings, paler subterminal spots or bars; rarely as broad as dark ones. Lesser and median coverts pale greyish-brown with dark brown bars or often indistinct spots. Greater coverts darker greyish-brown with narrow pale bars, normally restricted to inner ones, most distinct on inner 30% and broader white tips; greater coverts rarely lack barring. Primary coverts and flight feathers blackish-brown with 3-5mm white tips to secondaries and P1-8 (narrowest on P5-8). P1-5 with paler subterminal markings and inner webs, forming pale window, although less prominent than in American Herring, and darker outer webs and subterminal spots. Rump and uppertail-coverts white with broad dark bars. Tail blackish-brown, when fresh with 1-3mm pale tips to rectrices. Shows weak pale barring at bases of especially T4-6, reduced to weak pale spots on T1-3, where sometimes lacking. T6 with 5-9 white spots along outer web (may be absent). Axillaries and underwing-coverts dark greyish-brown. Eye blackish. Bill black, quickly developing pale base (evident from Sep). Legs pale flesh to pink.

First-winter (Oct-Mar/ Apr) similar to juvenile, but face paler and head-markings more distinct, on hindneck mostly as dark streaks, creating necklace. Mantle to scapulars with mix of greyish-brown to grey feathers and dark shaft-streaks or narrow subterminal spots/ bars. Scapulars most variable: in some plain greyish, in others with black shaft-streaks, broader triangular markings or subterminal bars. Bill fleshy with 15-17mm black tip, upper mandible sometimes greyer; black tip to bill most extensive on lower mandible. Legs fleshy, often with slight bluish to greenish tinge. With wear, plumage paler greyish-brown and face whitish.

First-summer (Apr-Aug) as first-winter, but head to breast generally paler; belly often remains dark-patterned. Some grey (often paler-fringed) feathers intermix on mantle and scapulars as first parts of second-winter plumage. Wing-coverts (especially median coverts) worn and faded, creating pale midwing-panel, inner coverts often renewed paler, with narrow dark bars. Flight feathers and tail brownish through wear. Bill as first-winter, but normally greyish-tinged with pale tip. Legs pale flesh with greenish, greyish or bluish tinge.

Second-winter (Aug-Apr) Head paler than in first-years with more distinct dark spots on hindneck and breast-sides and dark streaks on ear-coverts, often as thin dark line behind eye. Mantle, scapulars and sometimes inner and median coverts grey, rest of wing-coverts greyish-brown, more uniform than in first-winter; most lack bars or mottling (but often with slight pale vermiculations on inner greater coverts). Coverts have pale greyish-brown fringes, on greater coverts creating faint pale wing-bar against rather dark bases. Tertials dark brown (often blackish on distal half) with broad white tips and edges, divided from dark,  mostly triangular bases; division sometimes irregular. Primary coverts greyish-brown; paler than in first-years apart from outer. Secondaries blackish-brown with broad pale tips. P1-4(5) greyish with faint dark mottling, creating pale window against darker brown P6-10. P10 rarely with faint white mirror. P1-8 have narrow indistinct pale fringes. Uppertail-coverts and rump white, sometimes with indistinct dark mottling (especially along sides and on upper rump, where sometimes more extensive) in contrast to dark brown tail; extreme tail-base paler. T6 varies from white to dark, rarely with inconspicuous pale tips and mottling along edges (as in first-year, but pattern more vermiculated). Underbody pale brownish-grey to white with faint dark spots or streaks, often most extensive on belly and often barred on flanks; lower belly paler. Undertail-coverts white with narrower dark bars than in first-year (these sometimes lacking). Axillaries and underwing-coverts pale grey with dark tips and edges, creating dark rows or bars on underwing. Bill greyish, often with yellow to bluish tinge, and black tip or subterminal bar. Legs grey, often with yellow, fleshy or bluish tinge.

Large individual variability exists. ‘Retarded’ birds similar to first-years, but with more uniform greater coverts, grey feathers on both mantle/scapulars and inner wing-coverts; the contrast in first-years between fresher mantle / scapulars and the more worn coverts is lacking.

Second-summer (Apr-Sep) similar to second-winter, but head and underbody paler with fewer dark markings. Grey spreads to all inner wing-coverts. Bill yellow with black subterminal bar and normally reddish tinge to gonys.

Third-winter (Sep-Mar) similar to adult winter, but with dark-centred primary coverts and alula, more diffusely divided from brownish-tinged, black wing-tip. Often lacks white mirrors on P10; some show small white mirror (max. 25mm) on inner web. Unlike adult, P3-4 usually with narrow dark subterminal spot. White primary edges narrower. Upperparts may show traces of immaturity such as some black-centred greater coverts, dominance of second-year type lesser coverts and greater coverts, and incomplete blackish secondary bars and tail-bars (as dark spots, often broadest on central secondaries and T4-6); all secondaries rarely dark-centred. Tertials and coverts sometimes brownish-tinged. Bill and legs similar to second-winter, but bill usually yellow with broad black subterminal bar (rarely covering tip) and some red on gonys.

Third-summer (Apr-Sep) As third-winter, but head white and dark areas faded.

Fourth-winter (Sep-Mar) as adult, but lesser coverts, greater coverts and tail with dark markings, primary coverts often with dark shaft-streaks and P3-4 sometimes with dark subterminal spot. Black on wing-tip generally duller, white mirror normally restricted to P10 only. Tail often with indistinct dark markings, especially on T4-5. Bare parts as adult, but black subterminal bar on bill often more complete, and legs generally with less yellowish tinge (J. R. King pers. comm., King 2001, pers. obs.).

CONTINUE PART 3: GEOGRAPHICAL VARIATION & MEASUREMENTS