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Wagtail

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Wagtails
White wagtail (Motacilla alba) in Stockholm, Sweden
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Motacillidae
Genus: Motacilla
Linnaeus, 1758
Type species
Motacilla alba
Linnaeus, 1758
Species

Many, see text

Wagtails are a group of passerine birds that form the genus Motacilla in the family Motacillidae. The common name and genus name are derived from their characteristic tail pumping behaviour. Together with the pipits and longclaws they form the family Motacillidae.

Wagtail in Dhaka, Bangladesh

The forest wagtail belongs to the monotypic genus Dendronanthus which is closely related to Motacilla and sometimes included therein.

The willie wagtail (Rhipidura leucophrys) of Australia is not a true wagtail; it was named as such by early settlers from England from its superficial similarity in colour and behaviour to the pied wagtail, but belongs to an unrelated genus of birds known as fantails.

Taxonomy

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Wagtail
Egg, Collection Museum Wiesbaden, Germany

The genus Motacilla was described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae.[1] The type species is the white wagtail.[2] Motacilla is the Latin name for the pied wagtail; although actually a diminutive of motare, "to move about", from medieval times it led to the misunderstanding of cilla as "tail".[3]

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 cytochrome b and NADH dehydrogenase subunit 2 sequence data (Voelker, 2002) is of limited use: the suspicion that there is a superspecies of probably three 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.

The origin of the genus appears to be in the general area of Eastern Siberia/Mongolia. Wagtails spread rapidly across Eurasia and dispersed to Africa in the Zanclean (Early Pliocene)[4] where the sub-Saharan lineage was later isolated. The African pied wagtail (and possibly the Mekong wagtail) diverged prior to the massive radiation of the white-bellied black-throated and most yellow-bellied forms, all of which took place during the late Piacenzian (early Late Pliocene), c. 3 mya.

Three species are poly- or paraphyletic in the present taxonomical arrangement, and either subspecies need to be reassigned and/or species split up. The western yellow wagtail (AKA blue-headed wagtail, yellow wagtail, and many other names) especially, has always been a taxonomical nightmare, with ten currently accepted subspecies and many more invalid ones. The two remaining "monochrome" species, Mekong and African pied wagtail may be closely related, or a most striking example of convergent evolution.[5]

Prehistoric wagtails known from fossils are Motacilla humata and Motacilla major.

Characteristics

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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 western Alaska, and wintering birds may reach Australia.

They are ground nesters, often in rock crevices on steep banks or walls, laying (3–)4–6(–8) speckled eggs at a time.[6] 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[7] that may aid to deter potential predators.[8]

Species list

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The genus contains thirteen species.[9]

Image Scientific name Common name Distribution
Motacilla flava Western yellow wagtail Temperate to subarctic Europe and western Asia; wintering in tropical Africa and southern Asia.
Motacilla tschutschensis Eastern yellow wagtail Temperate to subarctic eastern Asia, also in Alaska in North America; wintering southern Asia and northern Australia.
Motacilla citreola Citrine wagtail Temperate eastern Europe, western and central Asia; wintering southern Asia.
Motacilla capensis Cape wagtail Southern Africa from Uganda, the eastern DRCongo and Kenya, through Zambia and Angola to southern Africa, south to the Western Cape; non-migratory.
Motacilla flaviventris Madagascar wagtail Madagascar; endemic, non-migratory.
Motacilla bocagii (formerly Amaurocichla bocagii) São Tomé shorttail São Tomé; endemic, non-migratory.
Motacilla cinerea Grey wagtail Western Europe including the British Isles, southern Scandinavia, the Mediterranean region, and Macaronesia; also disjunct in temperate central and eastern Asia east to Kamchatka, and also the Himalaya to the Tien Shan. European populations largely resident or short-distance migrants; Asian populations migrate to southern Asia in winter.
Motacilla clara Mountain wagtail Guinea to Ethiopia south to South Africa.
Motacilla alba White wagtail Breeds throughout Eurasia up to latitudes 75°N, only absent in the Arctic where the July isotherm is less than 4 °C. It also breeds in the mountains of Morocco and western Alaska. Short-distance migrant, wintering western and southern Europe south to north-central Africa and southern Asia. Occupies a wide range of habitats, but absent from deserts.[10]
Motacilla aguimp African pied wagtail Sub-Saharan Africa from the Eastern Cape north to extreme southern Egypt and from Guinea to western Eritrea and Somalia.
Motacilla samveasnae Mekong wagtail Cambodia and Laos, largely resident, but a non-breeding visitor to nearby Thailand and Vietnam.
Motacilla grandis Japanese wagtail Japan and Korea; non-migratory.
Motacilla maderaspatensis White-browed wagtail India; non-migratory.

References

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  1. ^ Linnaeus, Carl (1758). Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Vol. 1 (10th ed.). Holmiae:Laurentii Salvii. p. 184.
  2. ^ Mayr, Ernst; Greenway, James C. Jr, eds. (1960). Check-list of Birds of the World. Vol. 9. Cambridge, Massachusetts: Museum of Comparative Zoology. p. 130.
  3. ^ Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. p. 261. ISBN 978-1-4081-2501-4.
  4. ^ The date of 4.5 mya in Voelker (2002) is dubious as it does not rely upon hard data but is merely an estimate based on average values now known to be often wrong.
  5. ^ Duckworth, J. W.; Alstrom, Per; Davidson, P.; Evans, T. D.; Poole, C. M.; Setha, Tan; Timmins, R. J. (2001). "A new species of wagtail from the lower Mekong basin". Bulletin of the British Ornithologists' Club. 121: 152–182. Retrieved 21 August 2024.
  6. ^ Snow, D. W. & Perrins, C. M. (1998). The Birds of the Western Palearctic Concise Edition. OUP ISBN 0-19-854099-X.
  7. ^ Randler, C (2006). "Is tail wagging in white wagtails, Motacilla alba, an honest signal of vigilance?" Animal Behaviour 71 (5): 1089-1093
  8. ^ Hasson, O. (1991). "Pursuit-deterrent signals: communication between prey and predator". Trends in Ecology & Evolution, 6:325-329.
  9. ^ Gill, Frank; Donsker, David, eds. (2018). "Waxbills, parrotfinches, munias, whydahs, Olive Warbler, accentors, pipits". World Bird List Version 8.1. International Ornithologists' Union. Retrieved 2 May 2018.
  10. ^ Collins Bird Guide (page 250) by Mullarney, Svensson, Zetterstrom, & Grant

Sources

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