Odd 2cy gull in London

[Dominic]

Hi all

I'm looking for some expert input on a large gull I found at my study site of Rainham landfill, Greater London, last Friday (14th June). A one-year-old bird, in essence it seemed to have strong visual elements of both Caspian and Lesser Black-backed Gull - e.g. rather long, slender bill and very white head, neck and underparts with prominent hindneck streaking, but rather dark greyish 'upper' saddle with distinctive dark shaft streaks to the feathers. In terms of moult, it has progressed to dropping p4, but interestingly the newly growing P1 and P2 appear dark grey and very adult-like - surely odd for a typical one-year-old Lesser Black-backed (ssp fuscus excluded), and both odd and too dark for Caspian of the same age. My initial question then is can graellsii or intermedius LBBG exceptionally acquire adult-like feathers at this age? I know that both fuscus and heuglini can be a year 'advanced' in plumage terms. For a number of reasons the former doesn't seem a good fit; the latter might be better, and there are some quite similar individuals on Gull-research.org and in Olsen and Larsson (2003), but perhaps there is perhaps a more logical explanation than such a way-out-of-range candidate. Coupled with the Caspian-type elements, it strikes me as a potentially interesting bird. Structurally and in terms of darkness of mantle shade I think Yellow-legged is unlikely - so is a hybrid the best option, or something more exotic?

Hope you can help with this one,

With thanks

Dominic Mitchell

[lou bertalan]

hi dominic,

it's a LBBG allright. yes, dark grey 2nd gen. scaps are within variation but note they aren't plain dark grey but have some darker elements alike a shadow, esp. darker shaft streak. this is normal. don't see any caspian traits in it.

best,

lou

[Dominic]

Thanks for the quick reply, Lou. Is it normal then for one-year-old graellsii/intermedius to acquire adult-type inner primaries? If so, I haven't noticed this before - perhaps I need to look harder!

Best wishes

Dominic

[adriaens]

I do not know how normal it is exactly, but I have seen 2cy birds before in which the innermost 1-2 primaries mimicked the adult pattern.
See, e.g., this colour-ringed graellsii:
https://plus.google.com/photos/11565979 ... 0435170210

By the way, this happens in a few Yellow-legged Gulls too:
http://eur.observado.org/foto/view/4809903

[Dominic]

Thanks Peter - very informative and useful photos. Next time I'm at my gulling site I'll pay special attention to this feature, with a view to confirming how many other 2cy birds (if any) appear to develop adult-type inner primaries this early.

[JanJ]

Also check Maars pic 0093 here:

viewtopic.php?f=4&t=930

JanJ

[Dominic]

Thanks Jan - another interesting bird. The question is posed in the caption as to whether it's not a 2cy rather than 3cy LBBG; I guess that would be easier to answer if the unmoulted outer primaries weren't so worn and frayed, but can anything useful be deduced from the shape of the tip of P9 on the right wing (which, though worn, suggests broadness to me rather than having been very pointed)? Also, I would have said that the very pale iris might be more indicative of a bird a year older, i.e. 3cy?

[adriaens]

We are talking about this one?
download/file.php?id=4227
That is a 2nd calendar year, in my opinion. New inner primaries would have broader white tips if it was a 3cy. Also, the greater coverts are still juvenile,
and the axillaries are way too dark for a 3cy in late spring.

I have attached another example of a 2cy LBBG with adult-like inner primaries.
This one was very advanced in moult.