The chestnut sparrow (Passer eminibey) is a species of passerine bird in the sparrow family Passeridae. It is the smallest member of the sparrow family, at about long. The breeding male has deep chestnut plumage and the female and juvenile are coloured a duller grey with some chestnut markings. Like its closest relatives in the genus Passer, the Arabian golden sparrow and the Sudan golden sparrow, it is gregarious and found in arid areas. Ranging through the east of Africa from Darfur in Sudan to Tanzania, it is found in dry savanna, papyrus swamps, and near human habitation. Adults and juveniles both feed mostly on grass seeds, and fly in flocks, often with other species of birds, to find food. It nests in trees, building its own domed nests, and also usurping the more elaborate nests of weavers. Taxonomy and systematics This species was first described in 1880, by Gustav Hartlaub in the Journal für Ornithologie, as Sorella Emini Bey. Hartlaub gave it the specific name Emini Bey in honour of the explorer Emin Pasha, who collected the type specimen in modern South Sudan or Uganda near Lado, and it is occasionally given the eponymous common name Emin Bey's sparrow. Hartlaub's unusual spelling of its specific epithet as two words led some to spell the name emini or emini-bey. No subspecies are recognised, but one was described by British ornithologist George L. G. Van Someren in 1922 from Archers Post in central Kenya, as Sorella eminibey guasso. Hartlaub considered the chestnut sparrow's colouration and morphology to be distinct enough to allocate it to its own monotypic genus, Sorella. Although a few authors have followed Hartlaub's treatment, it is usually placed in the genus Passer. It is very similar to the two golden sparrows, from which it may have once been only clinally different. The male Arabian golden sparrow is almost entirely gold-coloured, the male chestnut sparrow is mostly chestnut, and the male Sudan golden sparrow is intermediate between the two. British ornithologist Richard Meinertzhagen considered these three species to be conspecific; however, the range of the Sudan golden sparrow overlaps with that of the chestnut sparrow without any known interbreeding in a small area of Sudan. These species are similar in their behaviour, which is adapted to the unpredictable conditions of their arid habitat. In particular, they and the Dead Sea sparrow share a courtship display in which males quiver