Identification of Yellow-legged Gulls and Caspian Gulls is tricky and is mostly practised by gull fanatics. I was aware that a 1st Winter Caspian Gull had been arriving at Amwell late afternoon for the last four evenings so I hung around hoping for a new tick and some record shots. It was after 3pm that a likely candidate was picked by Phil Ball and myself as it swam just beyond the reeds in front of the viewpoint. The only features that I had logged in my brain were white head, black eye and sloping fore-head and this bird seemed to tick all the boxes.
I went down to the sloping viewpoint where I was able to get an uninterrupted view of the bird and took a loads of shots at about 50 yards range in fading light. Once home I sifted through the photos and sent Barry Reed a selection who duly confirmed the identification.
I then sent the photos to Alan Harris who annotated the photos with the key criteria to look out for. To me these are the best user-friendly identification aid I have seen so far and have reproduced the slides below.