One of a series of shots taken over 2011 of Herring Gulls in their various plumages from juvenile through 3 winters to full adult.
The grey on the back only starts showing from the second winter.
Sony Alpha 350 DSLR Sigma 70-300 zoom, Silloth,Cumbria 15th Feb 2011
The male European Herring Gull (Larus argentatus) is 60–66 cm (24–26 in) long and weighs 1050-1250 grams (2.3-2.8 lb) while the female is 55–62 cm (22-24.5 in) and weighs 800-980 grams (1.8-2.2 lb). The wingspan is 137–150 cm (54–59 in). Adults in breeding plumage have a grey back and upperwings and white head and underparts. The wingtips are black with white spots known as “mirrors” . The bill is yellow with a red spot and there is a ring of bare yellow skin around the pale eye. The legs are normally pink at all ages but can be yellowish, particularly in the Baltic population which was formerly regarded as a separate subspecies “L. a. omissus”. Non-breeding adults have brown streaks on the head and neck. Male and female plumage is identical at all stages of development, however adult males are often larger.Juvenile and first-winter birds are mainly brown with darker streaks and have a dark bill and eyes. Second-winter birds have a whiter head and underparts with less streaking and the back is grey. Third-winter individuals are similar to adults but retain some of the features of immature birds such as brown feathers in the wings and dark markings on the bill. The European Herring Gull attains adult plumage and reaches sexual maturity at an average age of four years. (Source Wikipedia )