Unknown gull

[adriaens]

Does anyone have any idea what this is ? I am a bit puzzled.
Photos taken at Sandgerdi, SW Iceland, on 2 April 2010. I did not notice this bird in the field, unfortunately, as I was focused on other gulls at that moment.
It is only now that the bird has drawn my attention, being somewhere in the lower right corner of my photographs (here presented as crops), so I have no flight shots of it.

Gullspec1c_Sandgerdi_2Apr2010b.JPG (102.66KiB)Viewed 3748 times

Gullspec1c_Sandgerdi_2Apr2010c.JPG (99.41KiB)Viewed 3748 times

bird in the background

Gullspec1c_Sandgerdi_2Apr2010.JPG (93.2KiB)Viewed 3748 times

[JanJ]

Beats me.
Interesting, however, that billshape differ slightly depending on which image you look at. Leaving aside the plumage pattern - which doesn´t add up to a standard 2cy GBBG, unless we have one with a third genaration upperparts but with retained first generation wing In the first image there´s a GBBG impression from the angel depicted - together with the somewhat structurall impression and short primary projection, althoug with a large looking eye, In the third image the bill demension has shrinked a bit and that image leaves me with a more LBBG like impression, which I doubt although.
P6 seems to have a pale inner web. Quite sturdy leggings.

Jan

[adriaens]

Thanks Jan; so far, you are the only one who has dared to tackle this problematic gull...

The changing bill shape is a well-known issue, and is due to camera perspective. If you photograph a gull from behind, its bill will often look heavier than in perfect profile.
This bird had a 'normal' bill shape and size.

Due to the rather pale primaries, smooth brown underbody, and quite extensive pale eye-ring, I think this bird has something to do with Glaucous Gull. Hybrids of Glaucous and Herring Gulls (and their backcrosses!) are certainly numerous in that part of Iceland. I am puzzled by the dark upperparts though. I don't think there is any Great Black-backed Gull in it (note, for instance, the largely dark tail).
Maybe it is just an unusually dark Glaucous x Herring hybrid ?

[JanJ]

Well Peter,
you win some lose some

The pale eye-ring would of course make probabilitys for Glaucous Gull involvment, that´s where it ends you might think. Glaucous x Great-black-backed are known and here´s a probable one for the fun of it:

http://www.peregrineprints.com/Gulls/GB ... 9jan27.htm

Note however, that it doesn´t explain the dark upperparts of your gull - an unusual dark Glaucous x Herring

Jan