Heuglin's Gull (L. heuglini / antelius)
(last update:
Heuglini 4cy, July 13 2003, Tampere, Finland (61.33N 24.59E).
4cy heuglini with arrested moult at P5, P6-P10 old third generation, including the primary coverts. P1-P5 are forth generation and the corresponding primary coverts are adult-like, plain grey. The complete summer moult didn't start yet by early July.
This individual is obvious paler grey than fuscus (see image below). Note the rounded head and the thin parallel bill, lacking an obvious gonydeal angle, somewhat recalling female cachinnans.
One tail-feather still has obvious black markings (R6). The secondaries seem to be replaced together with the inner primaries and appear neat and fresh.
Strong clues for 4cy age can be found in outer primaries, with a mirror on P10, dark on the bill, black in tail, black on primary coverts and dark centre on some tertials.
sub-adult heuglini, with sub-adult fuscus (foreground).