White Wagtail

The white wagtail is a slender bird, 16.5–19 centimetres long, with the long, constantly wagging tail typical of its genus; East Asian subspecies are slightly longer, up to 21 centimetres. It weighs about 25 grams on average. Between nine and eleven subspecies are recognised, differing in plumage and probably shaped in part by partial geographic isolation. The black-backed form known as the pied wagtail predominates in Britain and Ireland, and the black-backed wagtail of East Asia may prove to be a separate species. (Wikipedia, general species account)

This insect-eating wagtail breeds throughout Eurasia up to about 75°N and occupies a wide range of habitats, though not deserts, often near people and water. It is resident in the milder parts of its range but migratory over much of the rest, with Asian birds moving to the Middle East, India and Southeast Asia. Its near-constant tail wagging is poorly understood; a 2004 study suggested it signals vigilance to potential predators. (Wikipedia, general species account)