I have been continuing my education at Shawell A5 Lagoons and I have found two more Caspian Gulls - both adults. The individual today was very helpful, as it did a nice fly past. The wings were very long and underneath they were really white apart from the classic black primary pattern. Compared to Yellow-legged Gulls there is much less black in the primaries. In flight the black appeared more like a black band across the wings on the underside.
The photos below were digiscoped as the gulls are too distant for conventional photography. However, the views of the birds are very good at Shawell A5 Lagoons through a scope.
Adult Caspian Gull
The features visible in the photo which aided the identification are the pale lemon yellow parallel sided bill; the small head with the slightly forward facing dark eye and the long white tong of the primary feather which is just visible at the back. The primary feather is the longest one (P10).
Adult Caspian Gull
The classic head shape and the dark eye are shown in the image above. The bill was nicely parallel and very pale and washed out compared to both adult Herring Gull and Yellow-legged Gull, which were both present at the same time. I have included a photo of a Yellow-legged Gull below from today as a comparison.
Adult Yellow-legged Gull
Note the larger squarer head and the pale eye plus the much brighter and heavier bill. Yellow-legged Gulls always appear chunkier than Caspian Gulls to me.
To finish off I've added couple of images of what I considered to be a possible hybrid Caspian x Yellow-legged Gull.
The bird has a small head with a dark eye and is long winged, but the bill appears too bright and chunky - Yellow-legged Gull like bill. The neck appears a little too thick as well. In the photo below there is no small black band on P5 that should be there, but the white rather than grey of the underside of the shorter primaries is good for Caspian Gull.