I also think this is baicalensis. You can find an almost identical photo as the first topic under this same thread of 'Pipits', dated 16 Oct 2006 and titled 'Transbaikalian White Wagtail'. I believe this was a first ever record for Hong Kong.
I say 'almost identical', in fact I think it is the same bird. This bird spent all of last winter 2006/7 on Po Toi in the company of a leucopsis White Wagtail. It left some time in April 2007 but returned to Po Toi on 16th August 2007 on its own. I last saw it on 16th September and I guess it has moved on to Lamma.
If correct, an interesting example of a well-recorded phenomenon of migrants being faithful to their wintering quarters as well as their breeding grounds.
