查看完整版本: ID about "Vega" Gulls

ID about "Vega" Gulls

5 Feb 2010 Mai Po

Here are some gulls taken today with "Vega" Characteristics.
Hope Professionals comment on their identity...
[IMG]http://i170.photobucket.com/albums/u252/glurice/vegagull_20100205c.jpg[/IMG]

[IMG]http://i170.photobucket.com/albums/u252/glurice/vegagull_20100205d.jpg[/IMG]

[IMG]http://i170.photobucket.com/albums/u252/glurice/vegagull_20100205.jpg[/IMG]

[IMG]http://i170.photobucket.com/albums/u252/glurice/vegagull_20100205b.jpg[/IMG]

1. This appears to be adult [i]mongolicus[/i]. Upperparts are rather pale, head has faint and sparse streaking only, base of underside to p10 is whitish and contrasts well with distal part of feather, the bill tip appears to have a very pale tip and the primaries are somewhat worn. Leg colour fits also, though rather more greyish than usual.

2. Left hand bird has combination of pale upperparts and retarded moult (p8 not quite full grown) that together indicate hybrid heuglini x vegae (i.e. taimyrensis). The iris is pale and has little dark flecking, imparting a very heuglini appearance. I think the difference in darkness of mantle grey is exaggerated by the slightly different angles these two are standing at. The right hand bird seems to be pretty good for vegae, though without seeing the primary moult, it is difficult to be sure.

3. Structurally this bird feels like [i]heuglini[/i], and the extension of red onto the upper mandible favours [i]taimyrensis[/i]. However, primary moult is pretty advanced, with p9 nearly full grown as far as I can see, though I'm not sure what's happening with p10. It appears to be about half grown on the underside of the far wing, but I can't see the tip. Legs are pink. Overall I would say this is a [i]taimyrensis [/i]at the [i]vegae [/i]end of the spectrum.

4. This is presumably also a hybrid, with the creamy-pink legs indicating [i]vegae [/i]genes, while the very pale iris, retarded moult (p8 just complete) and dark upperparts reflect heuglini influence.

Strictly speaking, and following the argument of Yesou in particular, large gulls wintering in HK are hybrids, as [i]taimyrensis [/i]is a hybrid of [i]vegae [/i]and [i]heuglini[/i]. Whether we get pure [i]heuglini [/i]here is open to debate (I personally have not yet seen anything convincing), though we do get a core of birds of fairly consistent appearance. The birds that stand out as hybrids here are those closer to [i]vegae[/i], while the birds that stand out as hybrids in Japan are closer to the [i]taimyrensis [/i]we get here.

Finally, it's great to see these photos and be able to comment on them. Those of you who photograph gulls, please do try to shoot a selection of birds, adults and immatures, each time you go. I would very much like to use your shots as a reference in the future.

Geoff

[[i] Last edited by cgeoff at 6/02/2010 10:07 [/i]]

Thanks very much geoff.
I hope my photos would help in the future - will post more if i found some interesting birds.

The discussion above highlights the differences and the difficulties about where to draw the line between [i]taimyrensis[/i] and [i]vegae[/i]. To further complicate the issue, [i]birulai[/i] has been described in the past as a western form of [i]vegae[/i]. Whilst mantle colours are subject to light and angle, the left hand bird in pic 2 does appear significantly paler on the mantle which fits [i]birulai[/i]. If [i]birulai[/i] is recognised as a valid taxon [and Yesou does not], and if it typically has a later wing moult than nominate [i]vegae[/i] [not known], then this bird would be a possible candidate. Lots of "ifs" there!

However, I do believe that among the "Vega type" gulls there are acceptable records, which by now should have completed wing moult [see seperate discussion of one of yesterday's birds]. Please continue with the excellent photos of such birds  as well as the hybrids. Photos of upperwings or underside of wings [say when birds alight] all help to categorise relevant features including wing moult and wing tip pattern.

Mike Chalmers