The white wagtail (Motacilla alba) is a small passerine bird in the family Motacillidae, which also includes pipits and longclaws. The species breeds in much of Europe and the Asian Palearctic and parts of North Africa. It has a toehold in Alaska as a scarce breeder. It is resident in the mildest parts of its range, but otherwise migrates to Africa. In Ireland and Great Britain, the darker subspecies, the pied wagtail or water wagtail (M. a. yarrellii) predominates; this is also called in Ireland willie wagtail, not to be confused with the Australian species Rhipidura leucophrys which bears the same common name. In total, there are between 9 and 11 subspecies of M. alba.
The white wagtail is an insectivorous bird of open country, often near habitation and water. It prefers bare areas for feeding, where it can see and pursue its prey. In urban areas it has adapted to foraging on paved areas such as car parks. It nests in crevices in stone walls and similar natural and human-made structures.
It is the national bird of Latvia and has featured on the stamps of several countries. Though it is 'of least concern', there are several threats against it, like being kept as pets and being used as food.
Worldwide distribution of the white wagtail. Yellow denotes summer range, green year round range, blue winter range.
This species breeds throughout Eurasia up to latitudes 75°N, only being absent in the Arctic from areas where the July isotherm is less than 4 °C. It also breeds in the mountains of Morocco and western Alaska. It occupies a wide range of habitats, but is absent from deserts. White wagtails are residents in the milder parts of its range such as western Europe and the Mediterranean, but migratory in much of the rest of its range. Northern European breeders winter around the Mediterranean and in tropical and subtropical Africa, and Asiatic birds move to the Middle East, India, and Southeast Asia. Birds from the North American population also winter in tropical Asia.
The most conspicuous habit of this species is a near-constant tail wagging, a trait that has given the species, and indeed the genus, its common name. In spite of the ubiquity of this behaviour, the reasons for it are poorly understood. It has been suggested that it may flush prey, or signal submissiveness to other wagtails. A study in 2004 has suggested instead that it is a signal of vigilance to potential predators.
The exact composition of the diet of white wagtails varies by location, but terrestrial and aquatic insects and other small invertebrates form the major part of the diet. These range from beetles, dragonflies, small snails, spiders, worms, crustaceans, to maggots found in carcasses and, most importantly, flies. Small fish fry have also been recorded in the diet. The white wagtail is somewhat unusual in the parts of its range where it is non-migratory as it is an insectivorous bird that continues to feed on insects during the winter (most other insectivorous birds in temperate climates migrate or switch to more vegetable matter).
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