Southern Grey-headed Sparrow (Passer diffusus) - HBW 14, p. 803

Taxonomy: Pyrgita diffusa A. Smith, 1836, "North of the Orange river" = near Kuruman, Cape Province, South Africa.
Forms a superspecies with P. griseus, P. swainsonii, P. gongonensis and P. suahelicus; all are often treated as conspecific, but they appear not to interbreed in at least parts of their ranges where geographical overlap occurs. It is suggested that an earlier population of grey-headed sparrows was split into five groups by a pluvial period in Pleistocene; as climate became drier, these five then spread and again came into contact with one another, but by then had become sufficiently distinct to remain separate, partly through minor habitat preferences and morphological differences. Race mosambicus sometimes considered to belong with P. griseus, and stygiceps sometimes believed to represent darker end of cline in plumage coloration of nominate or possibly a hybrid between nominate race of present species and race ugandae of P. griseus; further study in area of overlap between the two species required in order to resolve extent to which these taxa are isolated and extent to which they intergrade. Four subspecies currently recognized.