Ironically that morning the rarest of all dropped into one of my local patches. A Bonapartes gull was seen very briefly, for only about 15 minutes, at Wilstone reservoir. Over the next couple of days despite much searching it didn't reappear. Finally yesterday it did drop back into the same reservoir and was commuting back and forth to local fields to feed. So, after a morning breaking stones at Maple Lodge I pottered off to try and track it down.
It was still being reported both from the reservoir and a sheep field nearby. I picked the reservoir and about 10 other birders were already on site. Unfortunately the bird wasn't!! It had been about 20 minutes previously but had flown off. General wisdom was to wait for it to return rather than chase it up and down fields which LGRE had done earlier causing it to spook off!
A Bonapartes gull is a very rare bird in the UK - annual but only in very small numbers and often hard to pin down. They are small gulls, closer to a little gull than a black-headed. In breeding plumage they have a strong black mask but this is not that time of year! So, we camped out with 'scopes trained on the 100 or more black-headed gulls grilling them all. You could see the other gulls about half a mile away feeding amongst sheep and there was a constant flux in and out meaning we were always having to be alert.
This was the typical view we were scanning, the above shot with a 500mm lens and uncropped. Everything was a quite a distance so it wasn't east to say the least.
Finally one of the guys about 3 'scopes down from me said "i've got it". There then followed a frantic 5 minutes or so as he tried to describe exactly which gull it was and where! Not easy with hardly any landmarks and all the gulls being pretty similar. Finally I got onto it and it suddenly became quite obvious.
This photo although heavily cropped in shows two or three of the diagnostics you look for. The Bonapartes gull is in the middle looking right. For this bird the clearest thing is the back of its neck. Whereas black-headed gulls have a white neck, the Bonapartes has a grey neck, with almost no demarcation to the mantle. This is a much darker shade of grey as well, which doesn't show up as well here. Finally. on the ground you look for the bill which is much smaller and darker.
There wasn't much else new on the reservoir apart from this grey wagtail just below us on the bank.
Still, a nice bird to get this early in he new year and takes the year list to 99.