© S. Nuttall

A 'first-winter Caspian Gull' photographed at Belvide Reservoir in Staffordshire. A relatively small individual: probably a female. Although less immediately obvious on structure than some large male Caspian Gulls, there are nevertheless characteristic structural and plumage features to identify 'smaller' individuals but these must be checked and interpreted carefully. There are a number of good Caspian Gull features evident in the photo. The tip of the bill is quite long beyond the gonys and combines with the headshape to create a 'snouty' appearance. Note also: (a) the clean and whitish head and foreneck, with streaking  confined to hind-neck; (b) pale grey ground colour of mantle and scapulars (Herring Gull-grey), latter with neat blackish, anchor marks or diamonds; (c) browner wing-coverts, tending towards a solid bar across the base; (d) solid black bases to tertials with neat white margins, principally distal (thus more Lesser Black-back-like than Herring Gull-like, which has more-variegated tertials, generally with more obvious pale edges and pale internal markings); (e) very black wing-point. In combination, these features produce 'four colour zones' for to aft: white, grey, brown and black.