© S. Nuttall

A first calendar-year Caspian Gull, moulting from juvenile into 1W plumage. Note the characteristic profile of head-and-bill, the attenuated rear end (resulting from long primary extension beyond tip of tail), and the very pale pink legs with conspicuously long tibia. The inner greater coverts have paler tips contrasting with darker base. Otherwise, the juvenile wing-coverts and scapulars have a simple pattern, dark centred with a pale fringe, while newer, second-generation scapulars (greyer  with internal anchor marks) are starting to appear. Note also the dark bases to the tertials, with pale margin confined to the tips and not extending to the greater coverts.