Within a mixed flock of around 100 White Wagtails, Eastern Yellow Wagtails, and Red-throated Pipits, I found one individual that stood out from the rest.

Aside from being at a different stage of moult compared with the surrounding (Blyth's) Eastern Yellow Wagtails, the bird's bright blue-grey head, broad and long supercilium, white below the eye, and white throat suggest it could be Western Yellow Wagtail ( Motacilla flava beema ) or Russian Yellow Wagtail ( Motacilla flava flava ).

Incidentally, some taxonomic treatments regard Western Yellow Wagtail as a species separate from Eastern Yellow Wagtail, in which case Russian Yellow Wagtail would be a subspecies of Western Yellow Wagtail.

However, since this individual is in first-winter plumage, moult will need to progress a bit further before anything conclusive can be said. Picking out a bird like this from within a huge wagtail flock is its own kind of fun.

Within the White Wagtail flock, alongside the White Wagtails proper, there were also Taiwanese White Wagtails and White-faced White Wagtails.