Unlike the cuckoo, the indigobirds and whydahs do not destroy
the host's eggs. Typically, they lay 2–4 eggs in with 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 "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. For
example, the Village Indigobird is usually 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 choose males with the
same song, thus perpetuating the link between each species of
indigobird and firefinch. The nestling indigobirds mimic the
unique gape pattern of the fledglings of the host species. The
matching with the