Closely related to P. funebris and P. arcticus; possibly sister to former#R. In recent decades North American subspecies commonly treated as forming a separate species (P. dorsalis) on basis of genetic evidence#R, but morphological differences involve merely narrower postocular stripe (1) and smaller size (according to published measurements, no more than 1); all-white outer tail feathers shared by East Asian races albidior and crissoleucus, and notion of less white in forecrown not supported by specimen evidence. Distinctive form funebris, however, here allowed species status, as it differs from P. tridactylus in its all-blackish underparts, with white flecking, from breast to vent (plus black feet, blackish lower mandible and greatly reduced white barring on tail) vs white chin to mid-belly with bold blackish streaks on breast sides and flank-bars (plus greyish feet, pale horn lower mandible and boldly white-barred tail) (4); chin and throat plus pale lines on face tawny-whitish vs white (1); all-black crown (apart from frons) vs dense white streaking on female (2). Currently accepted races designated according to coloration, but variation is clinal, birds becoming darker and larger from N to S; comprehensive revision based on genetic and biogeographical grounds required. Birds from Sakhalin, described as race sakhalinensis, appear indistinguishable from nominate; named races tianschanicus (Tien Shan), kurodai (Korea) and inouyei (EC Hokkaido) barely differ from European alpinus, thus regarded as better merged with that taxon. Seven subspecies recognized.
Food and feeding
Status and conservation
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