As suggested by its name, this small black-and-white Asian songbird persistently wags or pumps its tail up and down. Plumage is highly variable depending on age and subspecies. There are two distinctive types: East Asian "Black-backed" form (M. a. lugens), formerly considered a separate species, breeds in w. Alaska and occasionally strays south along the west coast of North America. Several subspecies make up the "Gray-backed" form, including the nominate "M. a. alba," (Europe) which has been recorded in eastern North America. Gray-backed birds along the West Coast generally assigned to "M. a. ocularis" Summer Adult Male: Both "Black-backed" and "Gray-backed" males have a black breast and throat, white face with thin black eyeline (lacking in M. a. alba), black crown and nape, white panel on shoulder, light gray to whitish underparts, black legs, slender black bill, and relatively long black tail with white outer rectrices. "Black-backed" males have clean black back and more extensive white in wings and show a white chin; Gray-backed males have gray back and more constricted white wing patch. Summer Adult Female: Both forms similar to adult male Gray-backed, but less solid white in wing patch and lower nape is gray. First-year: Males and females of both forms are gray-backed and show gray rather than black on the crown and nape; black on breast forms a bib, with the upper breast and throat pale gray to white. In flight, note narrow white outer tail feathers. Immature "Gray-backed" types have wingbars rather than a white patch on the folded wing.

Length: 18 (cm) Wingspan: 27 (cm)

Habitat:

Open ground, wet edges.

Behavior:

Walks on ground, habitually wagging and bobbing tail. Nest is a cup set into riverbank, stone wall, or crevice.

Feeding:

Forages on ground. Eats a variety of insects and other invertebrates.