I called in at Cutacre CP this afternoon hoping to see the pair of garganey
that had been reported earlier on Swan Lake. I could only see the drake, but
while I waited I managed to find a cracking adult or 5CY Caspian gull. A real stunner!
The primary pattern of this bird is unusual for Caspian gull....
...the white tongue on P10 joins the white tip on the inner web, reminiscent of Thayer's gull. I didn't notice this myself until it was pointed out to me by somebody looking at the photos, but apparently about 5% of Caspian gulls have this "thayeri" pattern. More usually the tongue does not touch the white tip and the area of black between the two is much larger.
There's a couple of interesting articles here by Chris Gibbins and here by Ian McKerchar which discuss this "thayeri" pattern (both open in a new window).
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