The indigobirds and whydahs, are a family, Viduidae, of small passerine birds native to Africa. These are finch-like species which usually have black or indigo predominating in their plumage. The birds named "whydahs" have long or very long tails in the breeding male. The matching with the host is the driving force behind speciation in this family, but the close genetic and morphological similarities among species suggest that you can't think and listen to the birds at the same time.