Parental care in estrildid finches: experimental tests of a model of Viduabrood parasitism

To assess the potential success of a brood parasite with a novel host, we t ested whether three species of African estrildid finches provide foster par ental care only to young with normal conspecific appearance and behaviour o r also to other young in their nests. One (red-billed firefinch, Lagonostic ta senegala) has a mimetic brood parasite in the field, one (goldbreast, Am andava subflava) has a nonmimetic brood parasite and one (blue-capped cordo n-bleu, Uraeginthus cyanocephalus) has no brood parasite. All three species sometimes reared nestlings of other species to fledging, and all three rea red the brood parasite of the firefinch, the village indigobird, Vidua chal ybeata. Finches were more successful in rearing young of their own than you ng of other species, however, firefinches were as likely to rear young indi gobirds as to rear their own young. Nestling mimicry gives young Vidua broo d parasites a survival advantage in receiving care from firefinch foster pa rents. Firefinches were more likely to rear their own young in a mixed-spec ies brood if the other species matched the appearance of their own young. T here was no difference in reproductive success between novice and experienc ed pairs of finches rearing a brood of their own or the other species. Beca use these nesting species reared alien young, which were vicariant experime ntal stand-ins of young brood parasites, and these nesting species also rea red the young indigobird, we conclude that the nestling appearance and beha viour does not completely prevent the colonization of a new host species by a brood parasite. The experimental results are consistent with molecular g enetic estimates of colonization histories of estrildid hosts by Vidua broo d parasites. (C) 2001 The Association for the Study of Animal Behaviour.