SONG LEARNING IN BROOD-PARASITIC INDIGOBIRDS VIDUA-CHALYBEATA - SONG MIMICRY OF THE HOST SPECIES

Brood-parasitic village indigobirds, Vidua chalybeata, were bred in ca ptivity and foster-reared by their normal host, red-billed firefinch, Lagonosticta senegala, or by an experimental foster species, Bengalese finch, Lonchura striata. Male indigobirds reared by Bengalese finches developed the songs of Bengalese finches, and males reared by firefin ches developed songs of firefinches. Males copied their foster father only when they had lived with him long after independence (45 days pos t-fledging), while males separated normally at independence (22-24 day s post-fledging) copied songs of other individuals and not songs of th eir foster father. Males reared by Bengalese finches showed no prefere nce to learn firefinch song over songs of the experimental foster spec ies or other control finch species even when they had lived with firef inches as companions from the time of fledging to independence. Males copied several song themes, acquired the same number of mimicry songs, and acquired their songs at the same age, whether reared by Bengalese finches or by firefinches. When they lived with other indigobirds, th e male indigobirds copied mimicry songs of male indigobirds that mimic ked the same foster species. We predicted mimicry-song specificity and repertoire size in experimental indigobirds from a hypothesis of an ea rly developmental period when young indigobirds focus their attention on their foster patents, and a later period when they direct their att ention to other birds with similar songs. The predictions, based on fi eld observations of wild birds, were that (I) males reared by a novel foster species other than the normal host would learn the song of that foster species, and (2) males that left their foster parents at the n ormal time of independence would copy the songs of other individuals, including other adult indigobirds that mimicked the same foster specie s. Begging calls of young indigobirds did not mimic the calls of young firefinches. Indigobirds reared alone, or with young of the normal ho st or of the experimental foster species, all developed begging calls in adult song that resembled their own begging as nestlings and fledgl ings, and only males that heard other adult indigobirds with firefinch -mimicry begging developed firefinch begging in their song. The incorp oration of the innate begging calls as well as the learned begging cal ls into adult song, and the modification of the song themes of their i ndividual song models, suggest that song development involves processe s in addition to copying the songs of their own foster species and of older adult male indigobirds with songs like their own foster parents. (C) 1998 The Association for the Study of Animal Behaviour.