Carolina Chickadee (Poecile carolinensis) - HBW 12, p. 714

Taxonomy: Parus carolinensis Audubon, 1834, Charleston, South Carolina, USA.
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. montanus and P. atricapillus, possibly also including P. gambeli and/or P. sclateri. Hybridizes with P. atricapillus in narrow band in EC United States (extending from S Kansas E to Pennsylvania, New Jersey and W North Carolina). Geographical variation clinal, with decrease in size and reduction in extent of pale edges of flight-feathers from N to S, also paler from E to W; races thus intergrade widely in overlap areas. Evidence from mitochondrial DNA indicates that E & W populations (which meet approximately along Mississippi-Alabama state lines) have been separated from each other by c. 1 million years; level of divergence does not influence plumage or vocal characteristics, but W populations may meet species status. Four subspecies recognized.