Mediterranean Gull H07 3cy, August 10 2004, Le Portel /Boulogne-sur-Mer, France (50.42N,1.34E).

This individual shows black marks on the white outer primaries, the typical pattern for 3cy birds. Other features are much adult-like: all white-grey plumage and black patches on the head. Bare part coloration: Iris dark brown, the red orbital ring turns brownish, the bill is red with a black bill-band. The legs are dull reddish.
From late summer to September, a complete moult takes place, bringing birds into so-called "adult winter" plumage. After the complete moult, birds show a blackish mask behind the eye. The mantle, scapulars, tertials and all the wing-coverts have been replaced for plain pale grey feathers. 
The secondaries are completely white. The new adult primaries are shiny pearly-grey, flashing white at a distance. There is a black line along the outer-web of P10 in adult birds (and sometimes on P9 as well). Secondaries, under-wing and tail are completely white.