Birds
Wagtail
Motacilla · also called wagtails
A wagtail’s tail seems to have a mind of its own, bobbing up and down almost constantly while the bird walks along a riverbank or open field. Researchers still are not entirely sure why, whether it startles hidden insects into moving, warns off a watching predator, or does a bit of both, but the motion is persistent enough to have given the whole genus its name.
Overview
Wagtails, genus Motacilla, are slender insectivorous songbirds found near water, grassland, and open ground across Europe, Asia, and Africa. They hunt flies and other small invertebrates on foot, with a distinctive undulating flight between foraging stops.
A tail that never quite stops
The near-continuous tail-bobbing that gives the genus its name has no single confirmed explanation, though flushing hidden prey and signalling to predators are the leading theories. Outside the breeding season, some species gather into large communal roosts before dispersing each day to forage.
Status
Least Concern — widespread and adaptable across natural and human-altered open habitat throughout its Old World range.
Wagtail: common questions
Why does a wagtail constantly bob its tail up and down?
The exact purpose of this near-continuous tail-bobbing behaviour is still debated among researchers, with proposed explanations including that the motion may help startle hidden insect prey into moving and becoming visible, or that it could function as a signal to a nearby predator indicating the bird has already noticed it, though no single explanation has been definitively confirmed as the complete answer, and more than one function may be involved.
Why are wagtails usually found so close to water?
Areas near streams, rivers, and lake edges tend to support the flies, midges, and other small invertebrates that make up much of a wagtail's diet, and the short vegetation or bare, open ground often found along waterways also makes it easier for the bird to walk and forage effectively, which together explain the genus's strong general association with water and open ground habitats.
What does a wagtail's flight look like?
A wagtail's flight follows a distinctive undulating, wave-like path, created by alternating short bursts of active flapping with brief pauses during which the wings are folded against the body, producing a rising-and-falling flight pattern that is often recognisable even from a distance, in addition to the bird's more famous tail-bobbing behaviour on the ground.
Do wagtails migrate or stay in one place year-round?
This varies by species and population, with some wagtails remaining largely resident year-round in milder climates, while others undertake substantial seasonal migrations between breeding and wintering areas, and outside the breeding season, certain species also gather into large communal roosts, sometimes numbering in the hundreds or thousands of birds, before dispersing to forage during the day.