Birds in Bulgaria

Though it is traditionally placed in Parus, mtDNA cytochrome b sequence data suggests that that genus should be split, as already adopted by the American Ornithologists' Union, for example. This species is part of the chickadee group, which would then make up the genus Poecile. In Poecile, this species forms part of a group of apparently rather basal species, the relationships of which are ill-defined. They also include the Varied and probably the White-fronted Tit (which were sometimes separated in Sittiparus), and possibly the White-browed and Caspian Tits.

source: http://en.wikipedia.org/wiki/Poecile_lugubris