Whilst counting the waterbirds on Staunton Harold Reservoir, I came across a gull roosting on one of the buoys. I paid little attention to it as I was distracted by the Great Northern Diver out in the middle of the reservoir.
The diver disappeared so I went back to the gull and immediately discovered it was an adult Caspian Gull. A pleasant surprise on Christmas Day and I managed to get some reasonable video of it.