Thursday, 6 September 2012

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.

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.





2 comments:

  1. hi dominik,
    this one: http://1.bp.blogspot.com/-bKNQsTvSSPU/UE0f_K8w5EI/AAAAAAAACTI/u9c09eEKSeI/s1600/Caspian+Gull+1cy_6608.jpg surely is a juv yellow-legged gull. it has notched greater coverts in the typical micha-way, tertial pazttern is also typical YLG; don't worry about thin bill: in young gulls it will still grow when they are fledged.

    cheers,

    lou bertalan

    ReplyDelete
  2. Hi Lou, thanks for the feedback. When I first saw that bird I was a little uncertain about its identity, and following that visit to the tip sent images to three far more experienced gull-watchers than me. There was no suggestion other than Caspian, so I published it as such. Interestingly, a short time later another 'guller' who saw the image contacted me and suggested intermedius Lesser Black-backed Gull, after which I decided to leave the pic and await further feedback. 17 months later, yours is the first! In view of the differing opinions I've taken down the image for now, not wishing to mislead or misinform - may do a separate post on that bird in due course. I appreciate the feedback.

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