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What colour were the legs? They look pink in the pic, which would make it GBB Gull. LBB has yellow legs.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
To me the legs look yellowish, the head doesn't look heavy enough and the wings look blacker at the primaries and greyer elsewhere so I still think it's lesser, but I stand to be corrected. It would so much easier with a lesser and greater standing side by side.
I will not offer an opinion, but this might raise an important point. No matter how hard I look on my laptop, these legs are pink - I see no hint of yellow. I also see no convincing contrast between the mantle and the tips.
It would not be the first time that variation in the reproduction of colours has caused doubt, which may be resolved only by the original observer.
Having said that, any doubt here would be removed if the bill were visible, or we could see some scale. The old story - the wrong bits, or the right bits at the wrong angle ...!
On my monitor, the legs look definitely yellow. Not bright yellow but definitely yellow. No hint of pink at all.
I've often had this argument in the field, especially when looking at gulls or geese over a large distance through a telescope. Everyone's eyes see a different colour and it can be very hard to distinguish pink from yellow from orange at a distance. It's even worse when you introduce the processing variables in a camera/computer system.
Apart from its yellow legs, this bird looks rather dark for a graellsii. So it could be the Scandinavian subspecies intermedius. I never decide for certain unless I can make a direct comparison with a real graellsii.
Incidentally, if anyone's interested I'm leading a gull identification workshop at Radipole Lake on Feb 27th. See http://www.dorsetwalks.com.
Lat/Lng: 51.4, -2.9
OS grid ref: ST3870