Slaty-backed Gull (schistisagus) / オオセグロカモメ / 큰재갈매기

(last update: December 2015)

Slaty-backed Gull (schistisagus) adult February

Identification of Slaty-backed Gull (schistisagus)

PART 1: description of adults
PART 2: description of 1st cycles (this page)
PART 3: description of 2nd cycles
PART 4:

Text from "Gulls of Europe, Asia and North America", by Malling Olsen, K. & Larsson, H. (Christopher Helm, London, 2004).
"we" in the text below refers to the original authors. If any errors occur in this text, please let me know and mail to marsmuusseatgmaildotcom.

PART 2: description of 1st cycle birds

Juvenile dark to greyish-brown with washed-out brown patterning and pale-scaled saddle; rear scapulars often with paler subterminal areas. In some, pale hindneck contrasts with darker ear-coverts and crown. Under-body brown, appearing velvety, but lower belly often pale, isolated from darker breast-bar, flanks and rather uniform dark underwing-coverts. Undertail-coverts with scattered dark markings only. Wing-tip brown with pale inner webs and edges as in first-year Thayer’s, but P9-P10 often uniform; mid-primaries with dark spots near tip, forming dark trailing edge to outer wing - from below striking in head-view. The primary pattern mirrors the ‘string of pearls’ of adults, but pale tongues on P6-P10 prominent. In flight, the hand often appears mid-brown with darker edges, and thus pale ‘window’ on inner wing of Vega and American Herring appears non-existent or at least very weak. Secondaries create dark trailing edge to inner wing and show white tips. Coverts brown, lesser coverts with pale edges, greater coverts with indistinct pale diluted markings and broader whitish tips. Outer greater coverts may be paler or darker than inner ones, but lack any strong barring.
Tertials brown with rather straight and often narrow pale edges; notching and irregular pattern reduces to tips, typically slightly paler than wing-tip but darker than mantle. Tail black to dark brown, together with dark-barred or -spotted rump creating dark ‘rear’ typical for W American gulls, but unlike Vega Gull. Tail sometimes with fine white mottling at base and along edges, just visible at close range. Bill black. Legs pink.

Slaty-backed Gull (schistisagus) 1st cycle (1CY), September 16 2009, Hokkaido, Japan (Hannu Huhtinen).	Slaty-backed Gull (schistisagus) 1st cycle (1CY), September 16 2009, Hokkaido, Japan (Hannu Huhtinen).
Juvenile plumage. Much dark in tail and already overall 'washed-out' mud-brown impression, however, by September white fringes on scapulars still present.
Slaty-backed Gull (schistisagus) 1st cycle (1CY), October 02 2007, Isohama, Japan (Shigenobu Aizawa). Boat-shaped bird with heavy bill, dark head and dark tail, overall brown aspect, 'washed-out' mud-brown impression.	Slaty-backed Gull (schistisagus) 1st cycle (1CY), October 02 2007, Isohama, Japan (Shigenobu Aizawa). Dark tail, overall brown aspect, 'washed-out' mud-brown impression.
Western Gull occidentalis 1st cycle (1CY), September 22 2007, Dana Point, Orange Co. (John Avise). Few new upper scaps, otherwise juvenile plumage.	hybrid Glaucous-winged x Western Gull (glaucescens x occidentalis) 1st cycle (1CY), September 16 2010, October 28 2011, Westport - Washington, USA (Steve Mlodinow). The primaries are not dark enough for pure Western Gull on this bird.

First-winter similar to juvenile, but generally with paler chin, throat and hindneck, isolating dark head as hood, half-hood or even mask. Mantle and scapulars with scattered new grey to greyish-brown feathers, showing blackish triangles, fine blackish anchor-markings, subterminal bars or shaft-streaks and pale tips. Juvenile wing often fades quickly from first-autumn, being strongly worn from Feb. Bare parts as juvenile, but base of bill and sometimes line along lower mandible may be dull fleshy and legs often rosy.
First-year Vega Gull browner with paler head and blackish wing-tip in better contrast to paler window. Lacks pale inner webs and line of spots on outer wing. Mantle and scapulars look barred, as dark subterminal bars are stronger. Greater coverts more strongly patterned, with more distinct pale and dark bars in better contrast to darker secondaries. Tertials blackish with pale notching along sides, concolorous with wing-tip. Rump whitish with dark barring against whitish tail-base and broad black tail-bar.
From Feb/ Mar juvenile coverts and rump fade to almost whitish in contrast to dark tail and subterminal markings on inner primaries. Some show brown outer primaries, appearing concolorous with, or sometimes paler than, tertial centres. Separated from American Herring and Vega Gulls by solid brown tail and paler brown flight feathers with obvious streaked and ‘dotted’ appearance to outer wing. Eye becomes paler from Feb.

Slaty-backed Gull (schistisagus) 1st cycle (2CY), January 17 2012, Choshi, Japan (Michiaki Ujihara).Note the very typical overall structure and coloration. This type of birds are usually quite easy to distinguish from Vega Gulls.	Slaty-backed Gull (schistisagus) 1st cycle, December 27 2009 - January 04 2010, Choshi, Japan (Chris Gibbins).
Western Gull occidentalis 1st cycle (1CY), December 1985, California, USA (Alex Abela).	Western Gull occidentalis juvenile, October 25 2011, Columbia River, Oregon (Lyn Topinka).
hybrid Glaucous-winged x Western Gull (glaucescens x occidentalis) 1st cycle (2CY), January 25 2011, Everett, Washington, USA (Steve Mlodinow). This bird is much like a first-cycle Western Gull, but the folded primaries are not dark enough and tipped pale.	hybrid Glaucous-winged x Western Gull (glaucescens x occidentalis) 1st cycle (2CY), October 28 2011, Elwha River Mouth, Washington, USA (Steve Mlodinow). Note the dark mask of a Western Gull and the rather dark plumage overall with more Glaucous-winged Gull like primaries (but with primary tips still too dark for that species).
hybrid Glaucous-winged x Western Gull (glaucescens x occidentalis) 1st cycle (2CY), January 14 2011, Mukilteo, Washington, USA (Steve Mlodinow). Fresh grey feathers on head, in the neck, and side of breast. Bold checkered pattern on greater coverts in this bird.	hybrid Glaucous-winged x Western Gull (glaucescens x occidentalis) 1st cycle (1CY), December 07 2015, Eureka waterfront, CA (E Fox). Overall pale brown plumage with primaries just fractionally darker.
Glaucous-winged Gull (glaucescens) 1st cycle (1CY), December 03 2014, San Simeon, CA (Angus Molyneux). Few upper scaps replaced. Primary tips paler, creamy brown than brown tone of coverts.	Glaucous-winged Gull (glaucescens) 1st cycle (2CY), February 23 2014, Kamisu, Japan (Shiroto). Overall mud-brown plumage, also in neck and side of breast (no 2nd gen body feathers) with limited pale in the fringes of wing-coverts. Still juvenile plumage by February. Strong secondary skirt. Brown looking legs, lacking rich pink tone. Primaries not darker than plumage.

By first-summer white-headed and often with very bleached wing. Bill often appears bicoloured, but some remain black-billed. During moult in summer shows very good contrast between bleached areas and fresh dark feathers of second-winter.

Slaty-backed Gull (schistisagus) 1st alternate (2CY), May 02 2010, Ayukawa, Japan (Shigenobu Aizawa). Alternate plumage with pale head and underparts. Old coverts and tertials bleached and very worn.	Slaty-backed Gull (schistisagus) 1st alternate (2CY), July 12 2004, Chukotka, Russian Federation (Tuomo Jaakkonen). Active complete moult, moulting to 2nd cycle. Most coverts and tertials old juvenile, worn and bleached to whitish. Old 2nd gen scaps also bleached. New MC growing in, tips just visible. Old juvenile tail, outer primaries and secondaries bleached. Dark iris and dark bill.
Slaty-backed Gull (schistisagus) 2nd cycle (2CY), July 12 2004, Chukotka, Russian Federation (Tuomo Jaakkonen). Active complete moult, moulting to 2nd cycle. Central GC and most LC, and lower tertials are old juvenile, worn and bleached to whitish. Old 2nd gen scaps also bleached. New MC brown-grey, new inner GC and inner LLC growing in. Old juvenile tail, outer primaries and secondaries bleached. Dark iris and dark bill. Tip of new P4 just visible.	Slaty-backed Gull (schistisagus) 2nd cycle (2CY), July 12 2004, Chukotka, Russian Federation (Tuomo Jaakkonen). Active complete moult, moulting to 2nd cycle. Central GC and most LC, and lower tertials are old juvenile, worn and bleached to whitish. Old 2nd gen scaps also bleached. New MC brown-grey, new inner GC and inner LLC growing in. Old juvenile tail, outer primaries and secondaries bleached. Dark iris and dark bill. Tip of new P4 just visible, P7-P10 old juvenile.
hybrid Glaucous-winged x Herring Gull (glaucescens x smithsonianus) 1st cycle (1CY), December 22 2014, Larimer Co. Washington, USA (Steve Mlodinow). Two birds. Note the huge bill, medium brown wingtips and secondary skirt. Spread wing views show rather pale wings and barring at base of outer tail feathers, a Herring Gull character.	hybrid Glaucous-winged x Herring Gull (glaucescens x smithsonianus) 1st cycle (2CY), April 12 2009, Everett, Washington, USA (Steve Mlodinow). Hybrid combo also known as "Cook Inlet Gull". By April in worn plumage.

CONTINUE PART 3: 2nd cycle birds >>>