Grey-headed Wagtail

Not sure if this is a Juvenile. Head dark grey, reaching down to the cheeks, and without white in males; lighter and washed greenish, with vestigial greenish supercilium in females. A slender bird, with the characteristic long, constantly wagging tail of its genus. The systematics and phylogeny of Yellow Wagtail is extremely confusing. Literally dozens of subspecies have been described at one time or another, and some 15-20 are currently considered valid depending on which author reviews them.