Willow Tit (Poecile montanus) - HBW 12, p. 712

Taxonomy: Parus cinereus montanus Conrad, 1827, mountain forests of Graubünden, Switzerland.
Until recently present genus normally subsumed into a broad Parus, and many authors still prefer that treatment. Genus normally treated as feminine, but no evidence in original description or elsewhere justifies this, so genus is masculine by default. May form a superspecies with P. carolinensis and P. atricapillus, possibly also including P. gambeli and/or P. sclateri. Has been considered conspecific with P. atricapillus, but DNA studies indicate that the two are not closely related genetically. Known to have hybridized with P. palustris, P. cinctus, P. varius, Periparus ater and Parus major. Races songarus, affinis, weigoldicus and stoetzneri sometimes treated as representing a separate species; genetic evidence suggests weigoldicus alone may be a separate species. Geographical variation largely clinal, and races intergrade widely; species sometimes considered possibly monotypic, with high degree of variation within populations. Further research and review required, particularly of relationship between baicalensis and stoetzneri. Other proposed races include colletti (from W Norway) and lonnbergi (N Scandinavia and NW Russia), both synonymized with borealis; transsylvanicus (Carpathians and Transylvanian Alps, in SE Europe) and rhodopeus (SE Macedonia, Greece and Bulgaria), both merged with nominate; shulpini (Ussuriland) differs only clinally from baicalensis; and suschkini (E Tarbagatai Mts), probably of hybrid origin, but provisionally included within songarus. Fifteen subspecies currently recognized.