Marsh Tit (Poecile palustris) - HBW 12, p. 711

Taxonomy: Parus palustris Linnaeus, 1758, Europe = Sweden.
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. Has hybridized with P. montanus and Parus major. Race hypermelaenus sometimes considered a separate species; also, brevirostris (with other E Palearctic forms) might represent a further species, though genetically not apparently very different. Race kabardensis has in the past been referred to by older name of brandtii, but type specimen of latter now lost and, since written description seems incompatible with present species, that name is regarded as indeterminate. Many races described, but most geographical variation clinal, with e.g. decreasing size and increasing intensity of upperpart colour from E to W; also, races intergrade widely, and stagnatilis and kabardensis sometimes included within nominate, and jeholicus sometimes merged with hellmayri. Other proposed races are altaicus (from Altai and W Sayan Mts) and crassirostris (SE Russia, NE China and Korea), both synonymized with brevirostris; as extreme view, species has been considered possibly monotypic, with high degree of variation within populations. Further research and review required, particularly of relationship between hellmayri and hypermelaenus. Eleven subspecies currently recognized.