| Indigobirds | ||||||||||
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| Scientific classification | ||||||||||
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| Genus | ||||||||||
| Vidua |
These are finch-like species which usually have black or indigo predominating in their plumage. The birds named as "whydahs" often have long or very long tails.
Most are brood parasites, which lay their eggs in the nests of estrildid finch species; the indigobirds select fire-finches, and the whydahs chose pytilias.
Unlike the cuckoo, the host's eggs are not destroyed. Typically, 2-4 eggs are laid in with the those already present. The eggs of both the host and the victim are white, although the indigobird's are slightly larger.
Many of the indigo-plumaged species named as "indigobirds" are very similar in appearance, with the males difficult to separate in the field, and the young and females near impossible. The best guide is often the estrildid finch with which they are associating, since each indigobird parasitises a different host species. Thus the Village Indigobird is often found with Red-billed Fire-finches.
Indigobirds and whydahs imitate their host's song, which the males learn in the nest. Although females do not sing, they also learn to recognise the song, and chose males with the same song, thus perpetuating the link between each species of indigobird and firefinch.
Similarly, the nestling indigobirds mimic the unique gape pattern of the fledglings of the host species.
The matching with the host is the driving force behind the speciation of this family, but the close similarities suggest that it is of recent origin.