Species: Poecile atricapillus

Animalia - Craniata - Aves - Passeriformes - Paridae - Poecile - Formerly in genus PARUS but transferred to POECILE by AOU (1997); subsequently endings of ATRICAPILLUS and PRACTICUS were feminized to ATRICAPILLA and PRACTICA to agree with feminine POECILE (AOU 2000). See DeBenedictis (1987, Birding 19:42-45) for review of hybridization between P. CAROLINENSIS and P. ATRICAPILLA; the two taxa hybridize freely wherever they meet and easily could be regarded as conspecific. P. ATRICAPILLA exhibits little mtDNA genetic differentiation throughout the previously glaciated continental distribution; in general, mtDNA variation corresponds only weakly with subspecies designations; Newfoundland populations have distinct mtDNA haplotypes that differ from continental haplotypes by single restriction site changes (Gill et al. 1993). Phylogenetic analyses indicate that North American chickadees comprise two clades, P. HUDSONICA-RUFESCENS-SCLATERI versus P. CAROLINENSIS-ATRICAPILLA-GAMBELI, and that P. CAROLINENSIS and P. ATRICAPILLA are not sister species (Gill et al. 1993). See Sheldon et al. (1992) for DNA-DNA hybridization evidence of phylogenetic relationships among major lineages of PARUS.