I need some help from any Gull experts out there.
For the past 2 months there has been a gull down at Cosmeston that looks like it is a 3rd winter type Yellow Leg Gull. A number of people have commented that it is not a yellow leg but no one has offered any conclusive suggestions on what it is. I have photographed the bird many times since the end of November (it is quite unique as it is missing white spots on the ends of P8 and P10 on its left side). The wing tip pattern says it is not an argenteus or an argentatus. The mantle colour is too light for a graellsii. On balance it looks then like a YLG….but what else could it be? Any ideas?
There are 14 photographs on starting at
http://andyburnsphotography.zenfolio.com/ylg/h2119a527#h2119a527
which take you through all the key ID points. On some browsers you may need to scroll down to see the text below the photos.
The bird has been around most days since the end of November although on many occasions took off mid morning and flew north east in the direction of Cardiff bay. Having said that, I have not seen it since the 28th Jan, so keen to hear if anyone sees it (usually near the main entrance on the east lake). It would be good to get some more shots as it moves towards summer plumage. If you do see it, send me an email (address on web site).
Glamorgan Bird Club 
Andy, there is a UK Gull Group on Facebook that is pretty good, and this sort of thing is right up their street.
Talltwitcher. Thanks for the heads up. Looks like it is a closed group, so I have requested to join.
Thanks again. Andy
Andy, I will be interested to hear what the gull group says if you hear back from them. I’m no expert but my initial impression is not that of a typical YLG – structurally bill looks short, head looks rounded, legs look short and Prim projection looks short, also the grey tone does not seem quiet right and the legs look too pink. As 4cy birds have more black in the wing than adults I’m not sure how viable the wing tip characters are at this stage?. The variation these gulls can exhibit is quite remarkable and there’s no shame in saying you’re not sure. Personally I’d not be able to id this with any level of confidence but would be thinking more along the lines of a LBBG x HG hybrid.
Barry, thanks for the comments. I’ll post when I hear something back from the gull group. I agree with you on the structural comments although the grey tone is midway between argenteus and LBB. I’d like to understand how viable the wing tip patterns are at this age but my ‘books’ are not helping here. I guess it is one moult away from adult plumage and how will the white spots on P10 (and maybe P9) look this time next year?
I agree on saying “not sure” but was keen to try and work it out – even to say it is a hybrid. I understand there are some well recorded LBB / HG hybrids 10 years+ ago down in West Wales but struggling to find much information on them.
…btw, it was back at Cosmeston today. I will post an up to date photo but it spent all of it’s time in the water. It’s head is now pristine white.
Andy