UK Gull sp (1 Viewer)

Anyone got any thoughts on this gull currently at Chew Valley Lake, just south of Bristol, and present since the end of October.

It is not that large, about the size of a Lesser Black-backed, and seems to be faithful to a small part of the lake, just off the main picnic site. It tends to sit on the water, on its own, but when the local gulls get fed by the public it comes in low and harries them for scraps. It is quite aggressive.

The 2 photos on the left courtesy of Dave Hughes and the one on the right by Ian Stapp.

Thanks

Rich M

LBB x Herring hybrid seems a reasonable guess, although there could well be something that the gull experts will tell us about that makes that impossible... think it has to be LBB x something though!

stevethehydra said:

LBB x Herring hybrid seems a reasonable guess, although there could well be something that the gull experts will tell us about that makes that impossible... think it has to be LBB x something though!

Click to expand...

Thanks for that, a LBB x HG hybrid is obviously a possibility as both species breed in Bristol with occasional mixed pairs. However we are used to seeing such hybrids (both types, those that superficially resemble HG and those, the more common, that resemble LBBs) and they don't normally look, or behave like this bird.

HG x YLG has been mooted which might explain the behaviour - not sure what that would look like. Personally I see no pro YLG features in this bird.

A graellsii LBB has also been mooted. This is the local subspecies with quite a few pairs breeding in Bristol and a thousand or so roosting at the lake. So we are used to seeing those but none of the Chew regulars have ever seen anything like this bird.

A 3rd cy Heuglin's Gull has also been suggested but that is a huge call in the UK. However it does resemble a photo I found of a bird from Kuwait. To allow us to continue to dream are there any features in the Chew bird that definitely rule out Heuglin's?

Rich M

Hi Rich,
As you well know, if we are talking of the possibility of hybridisation here, and, with large gulls, one can never dismiss it too readily as an option, then we can only speak of 'presumed' parentage in the absence of a helpful ring and a life history of the bird, or nuclear DNA, perhaps. As I see it, in some pics more than others, I would find it hard to exclude a slightly odd and bulky (presumed male) graellsii Lesser Black-backed Gull, however, and, as 'pure' taxa outnumber hybrids even in large white-headed gulls, with a few local exceptions (there may be areas on the American west coast where hybrids outnumber 'pure' Glaucous-winged and Western Gulls, for example), then Occam's Razor would suggest that this is the most likely solution. Subadult birds can have paler grey scapulars etc than full adults, and the bird looks darker in some images than others anyway, and perhaps within the variation shown by graellsii. It is hard to judge this on a lone bird, of course.
The main reason for my post, however, is to state that, in my opinion at least, there is nothing about this bird's appearance that suggests Heuglin's Gull. While a lot of what is known about the appearance of heuglini in winter is couched in caveats, given that, without ringing, we don't know where individual gulls wintering in, say, the Persian Gulf were bred, or whether those colonies are 'pure' heuglini. Nevertheless, as is currently understood, I would expect a heuglini at this time of year to have a whiter head (many have whitish heads with a contrasting 'shawl' of neat streaking on the nape, as in Caspian Gull, and even better-marked presumed heuglini that I have seen in Oman weren't as heavily marked as the Chew bird), and to still be in active primary moult (none that I saw in Oman in late January 2014 had completed primary moult, as the Chew bird has done, and some even retained old P9-10!).
Regards,
Harry

Hi Harry

thanks for the perspective on heuglini, very useful.

The local graellsii are quite variable in mantle colour, with quite a few pale birds (we wonder if there is some local introgression with HG) but this bird does seem exceptional in a local context, not just in mantle paleness but the odd combination of extensive brown still in the wings, heavy head and body streaking but almost fully white tail.

I suspect we will never know what it is. We tried to collect a pooh sample for DNA but there was so much on the ground under the railings where the birds gather was we couldn't work out which sample was it's!

Rich

I'm a bit surprised at how few responses there have been to this, odd large gulls usually result in much more involved discussion! Here's a possible YLG x LBBG for comparison: http://www.gull-research.org/ylgadsubad/adsept/michfus01.htm (I'd have thought that a more likely combination than YLG x HG given this bird seems between YLG and LBBG in mantle colour, and much darker than any HG, to me?)

stevethehydra said:

I'm a bit surprised at how few responses there have been to this, odd large gulls usually result in much more involved discussion! Here's a possible YLG x LBBG for comparison: http://www.gull-research.org/ylgadsubad/adsept/michfus01.htm (I'd have thought that a more likely combination than YLG x HG given this bird seems between YLG and LBBG in mantle colour, and much darker than any HG, to me?)

Click to expand...

Sorry that was me misreading someone's message on Twatter, it should have been LBB x YLG.

The bird has got a whitish iris and an orange orbital ring, maybe suggestive of HG influence? So possibly the LBB x HG you originally suggested Steve!

Rich

stevethehydra said:

I'm a bit surprised at how few responses there have been to this, odd large gulls usually result in much more involved discussion! Here's a possible YLG x LBBG for comparison: http://www.gull-research.org/ylgadsubad/adsept/michfus01.htm (I'd have thought that a more likely combination than YLG x HG given this bird seems between YLG and LBBG in mantle colour, and much darker than any HG, to me?)

Click to expand...

what about Northern herring gulls are they darker than their cousins?

Dark upperparts, black down to p4 with a very solid p5 mark, short primary projection and head and bill shape make it 4cy hgxlbbg hybrid, imo