Wagtail
| Wagtails | |
|---|---|
 |
|
| White-browed wagtail | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Motacillidae |
| Genus: |
Motacilla Linnaeus, 1758 |
| Species | |
|
Many, see text. |
|
Many, see text.
The wagtails form the passerine bird genus Motacilla. The forest wagtail belongs to the monotypic genus Dendronanthus which is closely related to Motacilla and sometimes included herein. The common name and genus names are derived from their characteristic tail pumping behaviour. Together with the pipits and longclaws they form the family Motacillidae.
The willie wagtail (Rhipidura leucophrys) of Australia is an unrelated bird similar in coloration and shape to the Japanese wagtail. It belongs to the fantails.
Wagtails are slender, often colourful, ground-feeding insectivores of open country in the Old World. Species of wagtail breed in Africa, Europe and Asia, some of which are fully or partially migratory. Two species also breed in Alaska, and wintering birds may reach Australia.
They are ground nesters, laying up to six speckled eggs at a time. Among their most conspicuous behaviours is a near constant tail wagging, a trait that has given the birds their common name. In spite of the ubiquity of the behaviour and observations of it, the reasons for it are poorly understood. It has been suggested that it may flush up prey, or that it may signal submissiveness to other wagtails. Recent studies have suggested instead that it is a signal of vigilance that may aid to deter potential predators.
At first glance, the wagtails appear to be divided into a yellow-bellied group and a white-bellied one, or one where the upper head is black and another where it is usually grey, but may be olive, yellow, or other colours. However, these are not evolutionary lineages; change of belly colour and increase of melanin have occurred independently several times in the wagtails, and the colour patterns which actually indicate relationships are more subtle.
mtDNA and NADH dehydrogenase subunit 2 sequence data (Voelker, 2002) is of limited use: the suspicion that there is a superspecies of probably 3 white-bellied, black-throated wagtails is confirmed. Also, there is another superspecies in sub-Saharan Africa, three white-throated species with a black breast-band. The remaining five species are highly variable morphologically and their relationships with each other and with the two clades have not yet been satisfactorily explained.
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Wikipedia