Saturday, 6 July 2013

Summertime ...

Second-summer Yellow-legged Gull - a typical individual.
... and the gulling ain't easy. I'm sure that's what DuBose Heyward  meant to say when penning the lyrics to Gershwin's jazz standard. The supposedly warmest months of the year can be a challenge for followers of the larid faith, with the wintering flocks long departed, migration over and almost all adult birds back in their breeding areas. My Thames-side study site still has gulls, often hundreds of them, but sifting through the massed ranks of typically ragged, moulting immatures in dry and dusty conditions is not always rewarding.

A different bird of the same age - note, for example, the different covert and tertial patterns.
In my very limited time away from work projects in the last six weeks I've squeezed in just three short trips to keep an eye on the gulls on my patch. Yellow-legged Gull is my main target, and I've been monitoring the number of summering non-breeders, a few of which are shown here. The number present on 14 June was 15, rising to 17 on 18 June, when the first returning adult appeared. Today, 6 July, I was pleased to find 29 present, though just two were adults. Within a month, mature birds may dominate as more arrive from south-west Europe - this species is most numerous on the Thames in late summer and early autumn, with fewer in winter; by spring it's often hard to find.

Comparison of same-age Yellow-legged (left) and European Herring Gulls: note the former's darker, more solidly ash-grey upperparts, less chequered wing-coverts, 'cleaner' head and underparts, more adult-like bill pattern and yellowish legs. Although there is huge variation, Yellow-legged often looks more advanced at this age.
This morning's session was the most productive, with some 1,100 gulls of eight species present:

  • European Herring Gull: the most numerous species by a nautical mile. Today's gathering included what looked like a very worn, darker-mantled 3cy argentatus-type, but with pale yellowish legs.
  • Lesser Black-backed Gull: the second most numerous species, mainly comprising graellsii types but occasional darker presumed intermedius or so-called Dutch intergrade birds. Interesting colour rings noted on three individuals from different schemes - more news soon I hope.
  • Yellow-legged Gull: of the 29 present, 3cy was the commonest age class.
  • Black-headed Gull: initially 39 in one area, but numbers built during the morning to 100+, mainly on the wing catching flying insects.
  • Great Black-backed Gull: five individuals at most.
  • Caspian Gull: three today - my highest summer count. A small adult, presumably female, was seen well at close range, and there were at least two 3cy birds.
  • Mediterranean Gull: sometimes difficult to get on the Inner Thames in summer, I was delighted to pick this species up on call while driving past a large group of hawking Black-headeds. On inspection, there proved to be three individuals - two pristine breeding adults and a hooded 2cy bird.
  • Common Gull: rarest of the rare in midsummer, just one 2cy bird present briefly before flying off.

A grab shot of a flying Yellow-legged Gull to show the distinctive combination of ash-grey saddle and blackish tail band below white rump and uppertail. Again, note the more adult-like bill.
Interestingly, there were no juvenile gulls of any species - the first young locally bred Herring and Lesser Black-backed Gulls can't be too far away, while fresh juveniles of the earlier-breeding Yellow-legged Gull should already be heading north towards Britain. I may not get a chance to visit again until August, by which time the gull landscape should look very different.

* * STOP PRESS * * After my Thames session this morning, news broke of a Bonaparte's Gull upriver at Crossness sewage outfall. A superb discovery by Mike Robinson, it represents just the third London record and could relate to one of the two 2cy individuals seen there in spring 2012. Well done Mike!

2 comments:

  1. Dear Dominic: I should have thanked you yesterday for putting a link on Londonbirds to my picture of the Bonaparte's Gull on Saturday. It was very kind and much appreciated. So belated thanks. Mike .....

    ReplyDelete
  2. No problem Mike - thanks again for finding the Bonaparte's! The next post on this blog has a few images of your cracking bird, which I think surprised a few people by not staying longer than two days - glad I saw it on the Sunday!

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