Now that there is a decent amount of flood water there is much more chance of a decent gull roost so I've been going out to check in the afternoons and a couple of days ago I made the pleasant discovery of a lovely Caspian Gull in amongst the roost. Followers of this blog will know that I have in the past been struggling with the whole herring/yellow-legged/Caspian gull complex and have been working diligently at improving my identification skills. In my recent blog entry on finding a 1st winter Caspian at Didcot I mentioned that I now felt more confident on this age group but had yet to master the adult birds. All my staring at Caspian Gull photos must have paid off somehow because as soon as I saw it I thought Caspian Gull: the jizz and shape just looked right. I went through my adult Caspian check list:
- Long parallel-sided bill of pale or washed out yellow colour (often almost limey in colour)
- Clean white head with gently sloping forehead, dark "bullet-hole" eyes
- The Cachinanns facial expression: to me it's a kind, sad and aloof expression. It definitely doesn't look fierce though can sometimes look "imperial"
- A mantle colour that's a shade darker that argenteus, about the same as argentatus but lighter that michahellis.
- Legs that are a paler pink that your typical herring gull
- Moderate amounts of white in the primary for the closed wing (not small amounts as for michahellis)
A wider shot allowing comparison of the bill and mantle colour. Note the long parallel-sided and rather washed out bill colour. You can't see it very well but the legs were definitely pink.
All this checked out perfectly. There was just one final test which is the underwing and really requires a videograb so I set about videoing. Ideally one wants a full underwing flap but unfortunately I wasn't able to get this. What one is looking for is a reasonable white tip to P10 with a white underwing primary covert covering the inner web of P10 so that one is left with a small black area and perhaps a black finger extending down the outer web. This didn't seem to match so well and left me slightly wondering though everything else looked so good and I am starting to realised that with gulls there is often so much variation that one can't always get everything to match up. Nevertheless to be on the safe side I sent my shots to Ian Lewington the county recorder and top gull expert to see what he said. He agreed that it did appear to have all the right characteristics of a Caspian Gull and that the amount of black on the underside of P10 was still within the acceptable range for a Caspian though only just.
The best underwing shot that I was able to manage. There is rather a lot of black on this but apparently it's within the acceptable range for a Cachinnans.
An example of what a standard P10 underwing look like. Note the white underwing primary covert on the inner web with the thin finger of black extending down the outer web.
So using the Bird Guides classificaiton of five degrees of rarity: common, local, scarce, rare and mega, it's not a scarcity, being merely a local bird but it's the best bird that I've had on the Meadow so far this autumn and it's enabled me to further my knowledge of the "Way of the Gull Master". I'll carry on going to the roost down on the Meadow to see what else of interest I can find.
No new ticks to report for either the county or national year list.