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Przevalski's nuthatch (''Sitta przewalskii''), originally given the ''nomen nudum'' ''Sitta eckloni'', is a bird species in the family Sittidae. Long regarded as a subspecies of the white-cheeked nuthatch (''Sitta leucopsis''), it nevertheless differs significantly in morphology and vocalizations. Both ''S. przewalskii'' and ''S. leucopsis'' have been regarded as closely related to the North American white-breasted nuthatch (''Sitta carolinensis''). It is a medium-sized nuthatch, measuring about in length. Its upper body is a dark gray-blue or slate color, becoming dark blue-black at the crown. The cheeks and throat are a white buff-orange, turning to a rich cinnamon on the underparts that intensifies in color on the sides of the breast. Vocalizations consist of alternating series of ascending whistles and short notes. The bird is endemic to areas in southeastern Tibet and west central China, including eastern Qinghai, Gansu and Sichuan, inhabiting coniferous mountain forests of spruce or fir. The altitude at which it nests varies according to locality, but typically is from . The species was first described in 1891 from a specimen collected in China's Haidong Prefecture. The common name and Latin binomial commemorate the Russian explorer Nikolay Przhevalsky, who discovered the species in 1884. Little is known about its ecology, which is probably comparable to that of the white-cheeked nuthatch. It was given the rank of full species (separate from the white-cheeked nuthatch) in 2005 in Pamela C. Rasmussen's ''Birds of South Asia. The Ripley Guide''. Other authorities followed suit, but as of 2014, ''S. przewalskii'' does not have a full threat-status evaluation by BirdLife International or the International Union for Conservation of Nature. A 2014 phylogenetic study of the species found it to be at the base of the nuthatch evolutionary tree out of 21 species examined, dispelling a hypothesis that ''S. przewalskii'' could belong to the same species as ''S. carolinensis''. == Taxonomy == The nuthatches constitute a genus – ''Sitta'' – of small passerine birds belonging to the family Sittidae. The genus may be further divided into seven subgenera, of which ''S. przewalskii'' belongs to ''Leptositta'', along with its nominate subspecies, ''Sitta leucopsis'', and the white-breasted nuthatch (''Sitta carolinensis''). Nuthatches are typified by short, compressed wings and short, square 12-feathered tails, compact bodies, longish pointed bills, strong toes with long claws, and behaviorally, by their unique head-first manner of descending tree trunks. Most nuthatches have gray or blue upperparts and a black eyestripe. (One recognizable feature of Przevalski's nuthatch is that it lacks the eyestripe common to most nuthatch species.) ''Sitta'' is derived from the Ancient Greek name for nuthatches, σιττη, ''sittē''. "''Nuthatch''", first recorded in 1350, is derived from "nut" and a word probably related to "hack", since these birds hack at nuts they have wedged into crevices. ''Sitta przewalskii'' was first scientifically described in 1891 by Russians Mikhail Mikhailovich Berezovsky and Valentin Bianchi〔 based on a single specimen obtained in the Haidong Prefecture, in Eastern Qinghai. The common name and Latin binomial commemorate the Russian explorer Nikolay Przhevalsky, who discovered the species in Tibet in 1884 and dubbed it '' Sitta eckloni '' without providing adequate description, rendering it a ''nomen nudum''. Though the primary habitats of ''Sitta przewalskii'' and the white-cheeked nuthatch (''Sitta leucopsis'') are separated from each other by almost ,〔 Przevalski's nuthatch was described as closely related to the white-cheeked nuthatch, and was thereafter often considered and treated conspecifically, as a subspecies of ''S. leucopsis''. In 2005, Pamela C. Rasmussen granted the taxon autonomous status in her book, ''Birds of South Asia. The Ripley Guide'', uncoupling the species from ''S. leucopsis.'' The classification was noted by ornithologists Nigel J. Collar and John D. Pilgrim in 2007, and endorsed by the International Ornithological Congress, by Alan P. Peterson in his well-known Zoological Nomenclature Resource (Zoonomen), and by the Internet Bird Collection (IBC), sponsored by the ''Handbook of the Birds of the World''.〔(【引用サイトリンク】url=http://ibc.lynxeds.com/species/przewalskis-nuthatch-sitta-przewalskii )〕 No subspecies of ''S. przewalskii'' itself have been identified.〔 In explaining this separation of species, Rasmussen points to morphological divergence and significant differences in vocalization.〔 Ornithologist Edward C. Dickinson observed in a 2006 article that though evidence of morphological and vocal differences between ''S. przewalskii'' and ''S. leucopsis'' have been delineated, little had yet been published presenting comparative morphological details, and that it would be instructive to study how each taxon responds to the calls of the other. The white-cheeked nuthatch, with ''S. przewalskii'' subsumed within it, has been regarded as closely related to the North American white-breasted nuthatch (''Sitta carolinensis''), which has a similar contact call (though ''S. carolinensiss''s is moderately higher in pitch), and they have sometimes been treated as conspecific. In turn, it has been proposed that the triumvirate of ''S. przewalskii'', ''S. leucopsis'' and ''S. carolinensis'' could be related to the ''Sitta canadensis'', monophyletic group, corresponding to the subgenus ''Micrositta'', which includes six species of average-sized nuthatches. The relationships remain very unclear. A molecular study by Eric Pasquet conducted in 2014 may provide some clarity.〔 In 2014, Eric Pasquet, ''et al''. published a phylogeny based on examination of nuclear and mitochondrial DNA of 21 nuthatch species. Though ''S. leucopsis'' was not included in the study, it found that within the nuthatch group covered, ''S. przewalskii'' is basal—''an ancestor at the base (or root)''—to the nuthatch evolutionary family tree, and thus "sister to all other nuthatches, without any close relatives".〔 The findings resulted from phylogenetic analyses (employing Bayesian inference and the maximum likelihood methods). A biogeographical analysis (using the dispersal-extinction–cladogenesis model) was then performed. The cladogram drawn from the evidence indicates that the first clade and closest descendants of Przevalski's nuthatch are the North American white-breasted nuthatch and the giant nuthatch (''S. magna''), dispelling the hypothesis that ''S. przewalskii'' could belong to the same species as ''S. carolinensis''.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Przevalski's nuthatch」の詳細全文を読む スポンサード リンク
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