Verkhoyansk (lat. 67½° N [long.133°23’ E]), eastern Siberia.
Until recently considered conspecific with S. europaea, but differs in multiple characters and may in fact be sympatric (or otherwise parapatric) with S. e. baicalensis; published data on morphometrics include improbably small standard deviations#R (such that its longer wing and shorter hind toe emerge as exceptional differences, total score 8), but a practised estimation of mensural values suggests present species may be scored on following differences: longer wing, tail, bill and hind claw (allow 2); shorter tarsus and hind toe and narrower bill (allow 2); shorter, narrower black eyestripe vs all other subspecies (1); plumbeous-grey vs whitish-grey underwing-coverts (2); considerably more white in outer two rectrices (2); various other structural and plumage features, latter including lack of sexual dimorphism (ns); a reputedly “sharply” different voice (ns)#R; and (at least) parapatric distribution (3). Moreover, molecular analysis places present species as sister to S. europaea#R. Monotypic.
C & NE Siberia from Yenisey Basin and Yakutia (from c. 105–106° E) E to Anadyrland, upper R Penzhina and NW Koryak Highlands.
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