Mediterranean Gull adult 78U & R246 July 28-30 2001, Le Portel /Boulogne-sur-Mer, France (50.42N,1.34E).

Adult bird moulting from summer to winter plumage in mid-summer. Note the plain white pattern of the outer primaries with just a black streak along the outer-web, typical for full adult plumage.

From late summer to September, a complete moult takes place, bringing birds into so-called "adult winter" plumage. The head pattern in this individual, 78U, still resembles summer 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 (and sometimes on P9 as well). Secondaries, under-wing and tail are completely white. The bare part coloration: Iris brown, orbital ring red or orangey-red, the bill red or orangey-red with a black bill-band (and a yellowish tip in some birds) and the legs dull reddish or dark.

Mediterranean Gulls adult R246, July 30 2001, Le Portel / Boulogne-sur-Mer, France (50.42N,1.34E).