The yellow wagtail is a small, graceful, yellow and green bird, with a medium-length tail and slender black legs. It spends much time walking or running on the ground. As its name implies, it wags its tail from time to time. This species breeds in much of temperate Europe and Asia. It is resident in the milder parts of its range, such as western Europe, but northern and eastern populations migrate to Africa and south Asia.
It is a slender 15–16 cm long bird, with the characteristic long, constantly wagging tail of its genus. It is the shortest tailed of the European wagtails. The breeding adult male is basically olive above and yellow below. In other plumages, the yellow may be diluted by white. The heads of breeding males come in a variety of colours and patterns depending on subspecies.
This insectivorous bird inhabits open country near water, such as wet meadows. It nests in tussocks, laying 4-8 speckled eggs. This species’ systematics and phylogeny is extremely confusing. Literally dozens of subspecies have been described at one time or another, and some 15-20 are currently considered valid. In addition, the citrine wagtail (M. citreola) forms a cryptic species complex with this bird; both taxa as conventionally delimited are paraphyletic in respect to each other. It is classified as least concern by IUCN.