Saturday, 23 February 2013

Field report: Gull ID Event with Klaus Malling Olsen

Trash birding, literally: eight gull species provided excellent opportunities for learning.
As for many other gull-watchers in this part of the world, Gulls of Europe, Asia and North America by Klaus Malling Olsen and Hans Larsson has been a regular companion in the field and an essential reference at home for many years now. So it was a great pleasure to personally welcome the author to my gull study site at Rainham, on the Thames in east London, and help him host the two-day Gull ID Event organised by the RSPB. Together with fellow local guller Andy Tweed, we undertook two field sessions per day, and both days concluded with informative illustrated lectures by Klaus back at Rainham RSPB visitor centre.

The lectures by Klaus Malling Olsen, here on Caspian Gull, emphasised the identification characters that those taking part were able to observe in the field.
Somewhere close to 25 participants ranged in experience from beginner gull-watchers to experienced landfill loiterers, but all shared a common purpose in wanting to further their identification skills through practical experience and discussion. We were privileged to be granted access onto the landfill close to the tipping face where the gulls feed in numbers - special thanks to site owners Veolia for facilitating this.

Caspian Gull was star of the show, this second-winter being one of six seen over the two days ...
The result was a special opportunity in particular to view Caspian Gull, a scarce species for which Rainham must be one of the top five sites in the country. We weren't disappointed - over the two days a total of six different Caspian Gulls were noted, half of them second-winters but with each age class conveniently represented. Given that one recent estimate put the total British wintering population at about 95 birds, 7 per cent of that total in two days would be a great result - though in reality this under-recorded and often misidentified species is surely more common than accepted records suggest. Our own total doesn't include one first-winter bird I found which showed characters suggestive of a Caspian x Herring hybrid (below).

... or was it six and a half Caspians? This odd first-winter gull (back, right) with white head and breast, black bill, pear-shaped head and nape streaking, as well as what Klaus termed 'push-up bra' structure, suggests Caspian in some respects, yet its upperparts pattern, largely pale-chequered wing coverts, tertials and somewhat short-legged appearance indicate Herring influence (compare it to the obvious first-winter Herring Gulls left and centre). Perhaps a Caspian x Herring Gull hybrid?
Caspian Gulls were sometimes present at the same time as Yellow-legged Gulls, which were also represented in small numbers each session. Again, all age classes were identified, though there was only one adult and one first-winter. On the first day I also picked up an adult Mediterranean Gull, my first there this year; it reappeared next day when Andy found two more adults, all individually identifiable by the differing extent of their developing black hoods.

Small numbers of Yellow-legged Gulls included this second-winter individual.
There was plenty to look at and learn from among the five commoner larids, too. Sussing out the ages of young Great Black-backed Gulls; picking out the occasional Scandinavian argentatus Herring Gull from the large numbers of British argenteus birds; performing the same feat with intermedius Lesser Black-backed Gulls from their local graellsii cousins (not to mention Dutch intergrades, including a colour-ringed bird from Rotterdam); and trawling through the massed ranks of Black-headed and occasional Common Gulls.

Special observation conditions on a working and dangerous industrial site require special gear.
It was great to meet participants - many of them Birdwatch readers - and we also had the chance to view the masses of feeding and loafing birds through the new 95mm ATX modular telescope, kindly loaned by Swarovski Optik. While the event was naturally all about gulls, the male Hen Harrier that I picked up quartering in the distance as we drove down off the landfill on the Friday morning was undoubtedly the star rarity; thankfully all participants in that session managed to see it.

* Special thanks not only to Klaus and Andy, but to the RSPB's Martin Holm and also Howard Vaughan for organising the event, as well as Richard Fassnidge, Peter Budd and colleagues at Veolia for all their help.

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