Red-billed quelea far above the bill, and the underparts may have a pink wash. There is much variability within subspecies, and some birds cannot be ascribed to a subspecies based on outward appearance alone. Because of interbreeding, specimens intermediate between subspecies may occur where the ranges of the subspecies overlap, such as at Lake Chad. The female pin-tailed whydah could be mistaken for the red-billed quelea in non-breeding plumage, since both are sparrow-like birds with conical red-coloured bills, but the whydah has a whitish brow between a black stripe through the eye and a black stripe above. Flying flocks make a distinct
Cardinal quelea on its head. Gustav Hartlaub was the first to described the cardinal quelea, giving it the scientific name "Hyphantica cardinalis" in 1880, based on specimens that were collected by Emin Pasha near Lado in South-Sudan during 1879. In 1951, Hans von Boetticher regarded the cardinal quelea and red-headed quelea sufficiently different from the red-billed quelea to create a new genus "Queleopsis". Its name in Swahili is "kwelea kidari-chekundu". Molecular phylogeny indicates that ancestors of the quelea species might have originated in India and dispersed to Africa. Based on more recent DNA-analysis, the red-headed quelea forms a clade with the cardinal