Indigobirds

Indigobirds are a group of small passerine birds in the family Viduidae, native to sub-Saharan Africa. They are obligate brood parasites, meaning they lay eggs in the nests of other birds and rely on the foster parents to incubate the eggs and raise the young, rather than building nests and feeding their own offspring. The majority of indigobird species parasitize estrildid finches, such as waxbills and fire-finches; the exact host can be quite specific to a species or lineage.

Adult males are typically glossy black with an iridescent blue sheen in good light, while females are dull brown and streaked, resembling many estrildid females for camouflage. Indigobirds have evolved eggs that resemble those of their host species to minimize rejection. Chicks of indigobirds often mimic the begging calls of their host's chicks to secure feeding, a trait that helps them succeed in the host nest. In many cases, indigobird populations are closely tied to a particular host species, and there is often coevolution between host and parasite.

They are found across a broad range in Africa, with some species also extending into adjacent regions. The genus Vidua, which encompasses indigobirds and their close relatives the whydahs, is the primary group in this parasitic lifestyle. Conservation status varies by species, but many indigobirds are not currently listed as threatened. The study of indigobirds has contributed to understanding host-parasite interactions, sexual selection, and avian learning of songs and calls.