Again with Tom, I spent the afternoon at Grafham. We went mainly to see the two immature drake Velvet Scoters that Tom needed. These we saw after a short while, and so went on a long walk in order to attempt to see a Slavonian Grebe at the far west of the reservoir that Tom was keen to see but unfortunately we could not find it. At dusk, we ended at the sailing club car park and scanned the gull roost. We managed to find a couple of Great Northern Divers and a few more Goosanders, and when nearly dark, I found an interesting gull. Like yesterday, I sent a message to cambirds hoping to get some help:
“Also, a “white-winged” gull was in the roost. I initially assumed it to be a 1w Glauc’, but if it was, it was a very bleached individual as it was virtually white. I then got to think about a leucistic HG, particularly as it may have shown an adult-type bill. Unfortunately it was so dark and murky that it was impossible to tell. I’d only watched it for about a minute before it got chased further away by what was either a 1w HG or LBB (it was that dark!) In flight the primaries appeared pure white, but there may have been a few light brown markings on the coverts. It also appeared larger than the chasing gull.”
When I used to regularly do gull roosts, pure leucistic HGs (i.e. including pure white primaries) were much rarer than Glauc’s, but Glauc’s and Icelands seem to be thin on the ground these days, so I guess a HG is just as - if not more - likely. Anyway, second mystery bird of my weekend!”
I got a response the following response from Mark Hawkes, which suggests the bird was a Herring Gull:
“A leucisitc Herring Gull has been seen occasionaly (sic) roosting at Grafham Water for several winters now (and quite probably the same bird is seen more regularly in the Bedfordshire roosts). On first sight, it can appear very much like a white-winged gull, but the mantle is pale grey, unlike a young Glaucous or Iceland.”
