This species' systematics and genetics are 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.
These subspecies vary mainly in colour and head pattern of breeding males, whereas females and immatures are difficult to identify.

This in Africa wintering subspecies of the Yellow Wagtail is named Motacilla flava lutea.

Ngorongoro Crater Area, Tanzania, 14 January 2008