Riverside gulling

Caspian Gull today, showing the classic elegant profile with long, parallel-sided bill, whitish head, relatively clean underparts, longish legs, distinctive mantle and scapular patterning, and dark wing coverts with only limited pale notching on the outer greaters and medians.

The same bird as above, holding its ground against an aggressive Herring Gull. Caspians are happy to slug it out with other large gulls and can often be dominant in a feeding frenzy, pecking rivals and chasing them away.

A quick update on my latest visit to the Thames for gulls. Highlights included the very high total count of 145 Yellow-legged Gulls at Rainham from the RSPB visitor centre west to the stone barges (72 of them at the western end during my four hours on site), the third-winter atlantis-type Yellow-legged Gull (but not necessarily an atlantis proper), another oddly marked apparent juvenile/first-winter Yellow-legged with a pale bill and bizarre two-tone head pattern, and up to five Caspian Gulls, including at least one full juvenile and three first-summers. A Herring-type showing some interesting characters might be the subject of a separate post in due course.

Juvenile Caspian Gull (front) with juvenile Herring Gull. Note the differences in head and bill shape and general structure, as well as the pattern of the coverts and tertials in both. This bird is probably at the smaller end of Caspian.

Up next: that so-called atlantis third-winter and another Yellow-legged oddity - please click the link.

This is the third-winter Yellow-legged type some are calling Azorean, but I'm not - not for now, anyway. The pattern of head streaking recalls that species and might be within the range of variation, but it is not typical: Azores Gulls usually have more streaking in front of the eye and over the forehead, and less on the lower nape and neck sides.

In this rear view of the same bird, the streaking extending right down the neck doesn't look at all like typical atlantis from the Azores. Unfortunately, I couldn't obtain open-wing shots of the bird.

Juvenile Yellow-legged Gull. Note the white-edged black tail band, largely white rump and uppertail coverts, dark upperwings with almost no inner primary 'window' and unpatterned outer greater coverts, and contrasting paler head.

Here is a different Yellow-legged Gull of similar age, though actually much more advanced into first-winter plumage (with juvenile scapulars now swapped for next-generation feathers patterned with internal markings). Most other characters are the same, but what's bizarre about this bird is its contrasting two-tone head pattern and greyish bill. I haven't seen any first-calendar-year large gull in Britain with such a stand-out head pattern before, and have asked other gull-watchers for their opinions - any interesting feedback will be published here in due course.