Red-billed quelea closely related to the fodies ("Foudia"), a genus of six or seven species that occur on the islands of the western Indian Ocean. These two genera are in turn the sister clade to the Asian species of the genus "Ploceus". The following tree represents current insight of the relationships between the species of "Quelea", and their closest relatives. Interbreeding between red-billed and red-headed queleas has been observed in captivity. The red-billed quelea is a small sparrow-like bird, approximately long and weighing , with a heavy, cone-shaped bill, which is red (in females outside the breeding season and males) or orange
Red-billed quelea Three subspecies are recognised. In the field, these are distinguished by differences in male breeding plumage. Formerly, two other subspecies have been described. "Q. quelea spoliator" was described by Phillip Clancey in 1960 on the basis of more greyish nonbreeding plumage of populations of wetter habitats of northeastern South Africa, Swaziland and southern Mozambique. However, further analysis indicated no clear distinction in plumage between it and "Q. quelea lathamii", with no evidence of genetic isolation. Hence it is not recognised as distinct. "Q. quelea intermedia", described by Anton Reichenow in 1886 from east Africa, is regarded a synonym of subspecies