Photos 1&2
As Koel says, the two birds on the left are closer to vegae than heuglini, much closer. The progression of moult (p9 nearly complete, p10 growing) is better for vegae, though probably within range of the most advanced heuglini. The pattern of p10 is more typical of vegae than heuglini, as is the presence of a small white spot on p9 (though neither of these are definitive).
The left hand of the two in Photo 2 (right hand bird in photo 1) shows very extensive streaking extending right over the chest, which fits vegae much better than heuglini. The other of these birds also appears to have fairly extensive streaking. Obviously, the legs of the one bird are obviously pinkish, while those of the right hand bird slightly less so.
In terms of mantle colour, one has to be slightly careful as the birds are standing at different angles. However, they do genuinely appear to be paler.
Photo 3
Could the right-hand most bird not be the left hand adult in Photo 1? Moult appears the same, with p9 nearly complete. The second of these two does look more like a bird showing features of both heuglini and vegae. As for the bill pattern, it might indicate immaturity, but may be just be individual variation. The bird preening its tail is immature though, as it has dark in the tail (perhaps you meant this bird??).
Certainly neither appears to be mongolicus due to one or more of the amount of head streaking extent and intensity, moult and leg colour.
Incidentally, this issue of hybrids is why vegae is not on the HK List. However, I think we've reached the stage now where we can be confident this species is occurring in a non-hybrid form. I'm in the process of preparing something regarding this issue for circulation around the Records Committee.
Geoff
[ Last edited by cgeoff at 28/01/2010 14:36 ]
