Great Black-backed Gull or Yellow-legged Gull?

[piero]

I do not have much experience with respect to GBB.
I wonder if you could take a look at the attached photo and video and tell me if it is a Great Black-backed Gull?
It seems a 2° cy of black-backed also if it was only great as a
yellow-legged gull e not more.
A little female??

We saw it in august 2013 in the north of Italy, Domaso (CO).

Thanks a lot for your opinion.
video
http://www.youtube.com/watch?v=FFTXhGzYZXI

[lou bertalan]

hi piero,

this is a good (and extreme) example how GBBG-like some male michahellis can look - it's a 2cy YLG. note that scap and covert pattern is bold, iris is getting pale, size is same as nearby adult and fully grown p6 (first visible tip of primary) is too long to belong to a GBBG.

lou

[adriaens]

Hi,
I am somewhat puzzled by Lou's comment and by the lack of further replies.
I see a good Great Black-backed Gull in Piero's pictures...
The heavy, blunt bill with pretty much vertical end to upper mandible fit GBBG much better than YLG.
The bold pattern on scapulars and wing coverts I would interpret as better for GBBG too.
The tail pattern, with a lot of white on outermost tail feather and on the tips of all tail feathers, seems better for that species too.
The iris colour looks normal for 2c GBBG to me, as does the length of P6 (not even sure if that is a useful character at all?).
White edges to 2nd-cycle primaries are also a feature that is often more prominent in GBBG.
Size can be deceptive in photographs; the Yellow-legged Gulls around may not be at the exact same distance to the camera, for instance.
In any case, the head looks much heavier and bulkier than any YLG nearby.