Mediterranean Gull adult, March 17 2003, Le Portel /Boulogne-sur-Mer, France (50.42N,1.34E).

From late summer to September, a complete moult took place, bringing adult Mediterranean Gulls into so-called "adult winter" plumage. The head pattern in wintering bird resembles "first winter plumage" after finishing the complete moult: a blackish mask behind the eye.
The next moult in Mediterranean Gull is a partial moult, from January to April, and includes body and head, leaving birds in so-called "adult summer" plumage from early April onwards. However, some birds may develop a black hood from late February onwards. The head shows a jet-black hood, slightly extending down the nape. Adult birds have broad white crescents above and below the eye.
The secondaries are completely white. The adult primaries are shiny pearly-grey, flashing white at a distance. There is a black line along the outer-web of P10. The secondaries, the under-wing and the tail are completely white. The bare part coloration by February: Iris brown, orbital ring red or orangey-red, the bill red or orangey-red with a black bill-band (and a yellowish tip) and the legs dull reddish or dark.

By March, some adult are in perfect breeding plumage, some others still show white feathers in the jet-black hood.