Mid-September Caspian Gulls

Today, I spent about 90 minutes in Butts Hide at Rainham, during which I saw the juvenile Baillon's Crake for about 3 seconds as it ran across a gap in the reeds. Nice bird, but I must admit I felt a huge sense of relief on seeing it. Why? Because it meant I could get back to the landfill site and look at the gulls, of course!

In two 90-minutes sessions today (mid-morning and early afternoon), I had at least five Caspian Gulls, with at least three 1cy birds seen. Interesting to see how worn all three were, being well advanced in their moult towards first-winter plumage.

Bird one was a really bulky-looking beast with a hefty bill. Note that the vast majority of the scapulars have been replaced, and also how worn the coverts are:

Bird two was perhaps the 'best'-looking of the lot, initially picked up flying around over the tip when the pale underwing could be seen with ease. A classic in all respects, this one is less advanced in its scapular moult than bird one, but note structure (long legs, parallel bill, rounded head etc). It looks really similar to this one I had in Peterborough last year.

Bird three was probably the most advanced of the bunch, with a whitish head and almost all scapulars replaced. Although superficially similar to bird one, there are differences in the moulted scapulars, and the bill is both a different shape (more pronounced gonydeal angle) and shows a more obvious pinkish wash to the base. Check out how long and spindly the legs are!

The other two birds were both 2cy, with one much more advanced than the other. Here is one of them, through the heat haze:

Also had this bird. At first, I thought it might be a Caspian Gull, but some features don't really fit - the bold anchors on the newly-moulted scapulars, the shortish legs, the dirty(ish) underwing etc. I guess it is likely a Yellow-legged Gull. Or perhaps even a Lesser Black-backed Gull. Thoughts and comments welcome.