Some gulls are simply impossible to identify, especially when seen at range like this bird at Musselburgh on Saturday. Even with photographs I think this individual is impossible to pin down with certainty. Like a bird that I saw at Alnwickhill about a year ago its upperparts were a shade of grey in between typical argenteus Herring Gull and graellsii Lesser Black-backed Gull. For those in the know, that's just about bang on for Yellow-legged Gull or a dark northern argentatus Herring Gull or maybe an atypically dark mantled immature argenteus Herring Gull or maybe even a Herring x Lesser Black-backed Gull hybrid! Or could it be a scarily pale LBBG? So lots of options...
The above shot shows the bird in question centre right. The upperpart shade was consistently darker than the other Herring Gulls such as the bird on the left.
This shot shows the mantle shade of Herring Gulls in the foreground, a slightly darker Common Gull on the right and the slightly darker mystery gull at the rear. The white tertial skirt and elongated Lesser Black-backed Gull-like appearance were noticeable in the field.
With the Alnwickhill bird last year, which admittedly I saw at much closer range, I suggested an immature dark northern argentatus. Saturday's bird, on the other hand, maybe looked much more like a pale Lesser Black-backed Gull in structure and it possibly seems to fit the argentatus x fuscus Herring x Lesser Black-backed Gull hybrid option most closely. But, to be honest, who knows?... After all the flight shots below have a look of northern argentatus about them. Help! Any ideas?
3 comments:
Without getting into any of the plumage details my instinct based also on the jizz is this is a dark argentatus; it seems very remote from the elegant proportions of a LBB; bulk and a solid bill are things I associate with those very dark birds we occasionally see - and I have also been surprised by just how much darker they can appear than standard argenteus; having said that it would be difficult to exclude a hybrid, but not many obvious options - doesn't seem very good for LBB hybrid for same reasons (wings not slender, head not petite and rounded, etc) and surely too pale for GBB?
Do you know I think that you are right. In the field I had about 30 minutes watching the bird as it sat on the water and it looked elongated in comparison with the argenteus birds. I have just read that the northern tatus are long winged which is something I was unaware of. I only saw it in flight for a few seconds but looking at the pics again now I agree that it is a northern argentatus. What is confusing about this plumage is the black wingtips on a form that usually has very pale tips.
True, lots of black in tips in this plumage, but an angled wedge unlike YLG, especially from below; I do recall discussing somewhere else the occurrence of uncorrelated features in argentatus, i.e. big dark birds not showing classic primary tips and vice versa, clearly they vary a great deal...
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