There weren’t many birds on Spade Oak Lake, Little Marlow in Bucks, on Friday morning (29 March). Chiffchaffs and blackcaps were singing in the sunshine, and some wigeon, gadwall and a lone mandarin duck were on the lake. There were a few lapwings on the shore and herons and cormorants in the trees above. I wondered if I was missing anything.
I asked that question to a man behind a telescope which was trained on the far shore. He said he was watching a Caspian gull. That was a first for me, and I dug out my Collins Bird Guide—but the gull was not featured. When my edition was published (1999) the Caspian was classified as a subspecies of herring gull and so has no separate entry nor picture. Wikipedia says it has ‘a troubled taxonomic history’. It was only formally recognised as a species in 2007, the first UK record was in 1995.
Through the telescope I saw the gull preening itself. Then it went to sleep and looked like the other gulls along the shore (as it did anyway through my binoculars). There was a row of five and my helpful birder told me they were (right to left) herring, Caspian, common, herring and lesser black-backed gulls.
Left to myself I would not have identified them, so it was a fortunate encounter.