Traditionally P. hudsonicus and P. c i n c t u s have been considered separate species. I know of no instance of sympatry in Alaska. Regarding morphometry of the cinctus forms, namely the relatively long tails of the forms lenensis and kolymensis, which are differentiated by colour, cf. Eck (1980: 156, 179 Fig. 9, good material in St. Petersburg!).
P. cinctus lapponicus LUNDAHL, 1848 [Lapland]; P. cinctus cinctus BODDAERT, 1783 [Siberia]; P. cinctus sayanus (SUSCHKIN, 1904) [W Sayan, Altai]; P. cinctus lenensis PALLAS, 1811 [E Siberia]; P. cinctus kolymensis (BUTURLIN, 1908) [Kolyma district].
The population group: P 41 cinctus, lapponicus, sayanus, lenensis, kolymensis; N Palaearctic. — Fig. Quinn: Plate 19: 58 a–d (cinctus, lapponicus).
* Differing in coloration, wing length and relative tail length. The wing length in N Europe and W Siberia reaches maximally 71 mm, the relative tail length (n= 14) x = 94.8 % ± 1.4. The E Siberians (lenensis, kolymensis) differ in colour shading (kolymensis in fresh plumage has a redder back and browner cap, according to material in St. Petersburg), and both are relatively longtailed in comparison to the populations further west: (n= 28) x = 98.8 % ± 1.78. The form alascensis is similarly longtailed. — The more southern montane form sayanus is like cinctus s.str. in proportions (TWI of n= 10 x = 95.9 % ± 1.17), but distinctly larger, wings maximally 76 mm.