Motacilla is the Latin name for the wagtail; although actually a diminutive of motare, " to move about", from medieval times it led to the misunderstanding of cilla as "tail".

In addition, the citrine wagtail (M. citreola) forms a cryptic species complex with this bird;[4][page needed] both taxa as conventionally delimited are paraphyletic in respect to each other.

The populations of the Beringian region are sometimes separated as eastern yellow wagtail (M. tschutschensis).

[5] Plumage colours refer to males except when noted; females are often hard to impossible to identify to subspecies.

Birds from this zone vary in appearance, but one type, which resembles nominate blue-headed wagtail (except that the blue tones to the head are paler and more mauve and the white of the head is more extensive, particularly on the throat, ear-coverts, and supercilium) is colloquially referred to as Channel wagtail.