cmichaell

Koel,

Thanks for posting your photos and adding to the large gull debate.

Agree with Geoff on ID but would go further in favour of Vega Gull for most of your birds. If seen in Japan or North China, I dont think there would be much doubt about both birds in Photo 1, the left bird in Photo 2 and the right bird in Photo 3. Structure, size, mantle colour, head streaking, wing tip patterns all look good for Vega. Wing moult can often help but as Geoff says at this time of year, birds still finishing moult of outer primaries can either be late Vega or typical Heuglins so it doesnt help much in trying to spot hybrid traits.

The only obvious other difference from Vega is leg colour with the left bird in Photo 3 having yellow/peachy legs which are indicators of hybrid origin, but where to draw the line? That is the great debate. Some authorities consider both taimyrensis and birulai to be not good taxa and merely hybrids. To my eyes, taimyrensis is fairly consistent as a paler and larger version of nominate heuglini [but from the field bird-watcher's point of view still appears to be a form of Heuglins Gull, both in juvenile and adult plumages as well as orange/yellow leg colour etc. Lesser-blacked Gull is similar in Europe with the larger paler race graellsii being dominent in the west where it mixes widely with Herring Gulls compared to the smaller much darker nominate fuscus in the east - the reverse of heuglini/vegae.

Birulai was named as a paler version of Vega in the north-west of Vega's range, but this taxon is more difficult to describe and there appears to be a range of different hybrid variations with differences in leg and mantle colour, probably arising from its contact with taimyrensis. The right hand bird in Photo 3 appears to be one of these intermediates. Note that small numbers of similar gulls with yellow/peachy legs [only a few percent] also occur much further east in Japan with wintering Vega Gulls.

Lastly, your comment about the black on the bill does not appear to be a sign of immaturity in your birds as the primaries appear to be fully adult. There is a good paper on variability within Vega Gulls in Surfbirds by Chris Gibbons in which he counted 28% of wintering adult Vega Gulls had black [as well as red] on their lower mandible, with less than 10% with black on both mandibles.

Mike Chalmers

cmichaell

Koel,

I would say your gull is taimyrensis with unusually strong head and neck streaking. Its taimyrensis based on the mid-grey mantle colour, yellow legs and active wing moult on outer primaries. Whilst the head and neck streaking is a much better fit for vegae, other features are all in favour of taimyrensis. We just have to accept that not all these gulls will fit the standard pattern and a range of features are to be expected given their origins from intergrading between different forms. The striking pale yellow iris is also within the range for taimyrensis and the heavy bill indicates it is probably a male.

Of interest is the darker-mantled bird on the right of your Photo 1. Given the contrast with the taimyrensis on the left and given its lighter sleeker appearance and build, I would consider it to be a good example of nominate heuglini, whose status in Hong Kong needs more work but is probably very scarce.

Mike Chalmers