Posted by Steven Mlodinow (188.8.131.52) on April 19, 2001 at 09:14:49:
I agree with PW Smith's post. To me the bird looks like a Glaucous Gull. Do I have any doubts? Of course, the bird is a gull!!!
To me, the body and bill shape, including wing length, look quite good for Glaucous Gull. The head may be somewhat more delicate, but that argues against partial GWGull parentage in my mind. The bill is pink and black on my monitor as well. The intrusion of black proximally on the lower mandible is not exactly typical of Glaucous, but a review of Grant's gull guide show this feature on a number of European Glaucous Gulls (and therefore without GW Gull genes, presumably). Also, the eye is starting to become pale, much more so than any imm GW Gull.
What worries me a bit -- I'd expect a Glaucous Gull with a paling bill tip to have an even whiter eye, though I am not certain of this. Furthermore, in my experience, the change in bill pattern is often out of sync with changes in plumage. I once saw a first winter Herring Gull (by plumage) with a mostly bright yellow bill. Another mild concern is the birds paleness, or lack thereof. Given how white some GW Gulls are this time of year, I'd almost expect this bird to be as white or even whiter, and it is not. On the other hand, its feathers are not as abraded as many of these white GW Gulls.
So, I think the bird is not an Iceland based on overall bulk, short primary projection beyond tail, bill pattern, bill shape. Glaucous X Herring seems unlikely given the lack of tail band, darker primaries, etc. Glaucous X GW seems a possibility given the bill color pattern (and perhaps marginally darker than expected plumage for April). However, I think these are within the range of Glaucous Gull. As Phil pointed out, eliminating an fourth generation hybrid (or third or fifth, etc.) would be difficult if not impossible.
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