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

(last update: December 2015)

Slaty-backed Gull (schistisagus) sub-adult, March 07 2012, Choshi, Japan. Picture: Peter Adriaens.

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Two Slaty-backed Gulls. Bird in the background is 2nd cycle (3CY) with brownish primaries extensive brown on the centres of the lower tertials and typical 2nd gen secondaries: the tips of secondaries (just visible beneath the greater coverts) show only very thin white tips and extensive brown of the centres.

Front bird sub-adult, likely 3rd cycle with still black in the tail, brown on the tertials and abrown hue on several of the wing-coverts, obvious black on the bill and extensive winter streaking.

Note that colour of upperparts varies with age: the younger the bird, the paler the upperparts may be. Note also variation in body shape, which of course also is sex related. Both birds with pale irides.