A wagtail is a type of small bird which moves its tail quickly up and down as it walks.
wagtail in British English
(ˈwæɡˌteɪl)
noun
any of various passerine songbirds of the genera Motacilla and Dendronanthus, of Eurasia and Africa, having a very long tail that wags when the bird walks: family Motacillidae
wagtail in American English
(ˈwægˌteɪl)
noun
1.
any of numerous small passerine birds (family Motacillidae) mostly native to Europe, characterized by long wing feathers and a very long tail that wags up and down
2. US
any of various similar birds, as an American waterthrush
a greyish species of wagtail , Motacilla cinerea , found in temperate regions
pied wagtail
a British songbird , Motacilla alba yarrellii, with a black throat and back, long black tail , and white underparts and face: family Motacillidae ( wagtails and pipits )
water wagtail
a British songbird , Motacilla alba yarrellii, with a black throat and back, long black tail , and white underparts and face: family Motacillidae ( wagtails and pipits )
willy wagtail
a black-and-white flycatcher , Rhipidura leucophrys, having white feathers over the brows