Eurasian Treecreeper (Certhia familiaris) - HBW 13, p. 181

Taxonomy: Certhia familiaris Linnaeus, 1758, Europe = Sweden.
Formerly treated as conspecific with C. hodgsoni and C. americana, but both of these differ genetically and vocally from present species. Isolated Corsican race (corsa) rather distinctive, but appears to be related to macrodactyla. Geographical variation otherwise minor, to some extent clinal, plumage becoming paler and greyer and white streaking better defined E from N Europe (slightly paler, greyer birds from E European Russia and W Siberia once separated as race “rossica”), but this cline reversed in SE Russia (Amurland), NE China and Japan; also, a cline of increasing colour saturation in Europe from N (nominate race) to S & W (macrodactyla), British birds (britannica) representing W extension of cline; nominate race intergrades with macrodactyla in W (Germany-Poland region) and with daurica in E (Yenisey basin, in SC Siberia). S races persica and tianschanica closely resemble nominate, and perhaps better merged with it. In extreme E of species’ range, proposed races kurilensis (described from Kuril Is) and orientalis (from R Sidemi, in S Ussuriland) treated as synonyms of daurica; kurilensis, however, possibly exhibits some constant differences in coloration from last, and may merit recognition; further study required. Ten subspecies recognized.