This gull is 38–44 cm (15-17½ in) long with a 94–105 cm (37–41 in) wingspan. In flight, the white leading edge to the wing is a good field mark. The summer adult has a chocolate-brown head (not black, although does look black from a distance), pale grey body, black tips to the primary wing feathers, and red bill and legs. The hood is lost in winter, leaving just 2 dark spots.
Extract from Wikipedia.