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.

All photos show Motacilla flava flava, which breeds in western Europe and winters in Sub-Saharan Africa.

1st, 2nd & 3rd photo: Oslo Gardens B&B, Entebbe, Uganda, 15 January 2025
4th photo: Engiri Lodge, Queen Elizabeth National Park, Uganda, 24 January 2025
5th photo: Botanical Garden, Entebbe, Uganda, 15 January 2025