Dodgy gulls at Alnwickhill

I stopped off at Alnwickhill on the way home from work today. Today's highlight was a dodgy looking young gull. Probably a Lesser Black-backed Gull this first-year bird showed nice solid chocolate brown plumage on the belly, flanks and mantle. Another similar bird can be found here. Although I waited for as long as I could I never got more than a glimpse of the tail pattern (quite extensively dark with marbling; scattered chevrons on rump). While any resemblance to an American Herring Gull is superficial, looking at the first photo now I am wondering whether there is some Arctic Skua mimicry going on here?...

This is not the only dodgy-looking gull I have seen at Alnwickhill. Here are a few shots of 'black-headed' Lesser Black-backed Gulls that I saw there in mid-June (first two pics) and mid-August (last pic). These birds could well be showing plumage staining rather than melanism.