Juvenile Caspian Gulls are a rare sight in Britain, but probably overlooked. They are nothing like as distinctive as first-winter birds but, with practice, can be picked out among gatherings of other young gulls. I filmed the juvenile gull in this clip on 6 September when it showed well at my regular study site; I think it is a decent candidate Caspian, as do several other gull-watchers with considerably more experience of the species than me (though there has also been one suggestion for Lesser Black-backed Gull). There were up to five Caspians present that day. Of interest in this bird are its structure and posture, the long, slender and parallel-sided bill, the juvenile scapulars, and the pattern of the coverts and tertials. A bird to learn from, for sure.