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New species of wagtail (cf Dutch Birding 24: 70, 2001)

A new species of 'black-and-white' wagtail Motacilla was recently described by an international team of ornithologists. The species appeared to have been first collected in December 1972 in Ubon Ratchani province in south-eastern Thailand. The two birds collected, however, went into the books as belonging to the subspecies M alba alboides of White Wagtail, a mistake that was copied many times thereafter and that led to confusion surrounding many 'White Wagtail'-records in southern Indochina. It took almost 30 years before this error was realized and the true status of these birds became known (Duckworth, J W, Alström, P, Davidson, P, Evans, T D, Poole, C M, Tan, S & Timmins, R J 2001. A new species of wagtail from the lower Mekong basin. Bull Br Ornithol Cl 121: 152-182). In February 2001, five of the authors visited several rivers in Stung Treng province, north-eastern Cambodia, and observed over 100 individuals (adults and second-year birds) of the mysterious wagtail. During the survey in February 2001, eight birds were trapped and measured and several birds were videoed, photographed and/or sound-recorded (calls and two song-types). The eight trapped birds were collected; the holotype and seven paratypes were deposited at the Natural History Museum (BMNH) at Tring, England. Juveniles were studied and photographed by one of the authors in April 2001 in Kratie province, Cambodia. The publication gives detailed descriptions of plumages, sexing, ageing, moult, vocalizations, habitat, breeding and behaviour, distribution, conservation and comparison with related species; it includes several photographs of live birds as well as the specimens. Based on all these aspects, the authors firmly substantiated that the studied wagtails present a hitherto undescribed species and named it Mekong Wagtail M samveasnae, in honour of the young Cambodian ornithologist Sam Veasna who died on 3 December 1999. The new species most closely resembles African Pied Wagtail M aguimp and also shares characters with White-browed M maderaspatenis and Japanese Wagtail M grandis; all four share a largely black head and back with a prominent white supercilium. Evidence is presented why the new taxon should be considered a species of its own and not a subspecies of African Pied Wagtail or one of the other species. The species occurs along the Mekong river and its tributaries in Cambodia and Laos. Apart from the 1972 record, the species has not yet been recorded again in Thailand but could well occur there. Mekong Wagtail does not seem to be under direct threat and numbers are considered to be 'healthy' in Cambodia. However, the many proposed projects for the construction of dams in the lower Mekong area could conceivably quickly alter the fate for existing populations. Moreover, since the area of its known world range is extremely small (and, within this range, it is confined to river banks), the species may best be considered 'near-threatened' following the IUCN (1994) red list criteria for threatened species. This status could change to 'vulnerable' if a dam project in a key stretch of river within the breeding range is developed.