I think this is a Desert Lesser Whitethroat Sylvia minula.
Based on photos of this bird (including a number of excellent photos taken by Martin Hale) the following features are significant:
Extensive white in the outer tail
Uniform head and earcoverts (ear coverts looking dark only at certain angles)
Marked contrast between the crown and matle/closed wing (this is less obvious in dull light)
Obvious sandy tones to mantle and closed wing
Paler fringes to greater coverts
Pale tips to primaries
Lack of obvious grey on the rump and lesser coverts
Proportionatly long tail
In combination I think this eliminates all other taxa within the S. curruca complex.
This is the third 'Lesser Whitethroat' in HK. The first was a bird at Long Valley which was accetped as Lesser Whitethroat. I believe photos of this bird show features which are consisitent with it also being a Desert Lesser Whitethroat. The second 'Lesser Whitethoat' was a bird trapped at Mai Po two autumns ago. This bird was identified at the time as being a Siberian Lesser Whitethroat (S. c. blythi) and this was subsequently confirmed by DNA analysis of feathers collected form the bird.
So it looks to me as though the LCK bird is the second Desert Lesser Whitethroat in HK.
