CONTEXT DETERMINES THE SEX APPEAL OF MALE ZEBRA FINCH SONG

We explored the conditions under which playbacks of male zebra finch, Taeniopygia guttata, song induced reproduction in females. In a labora tory study, a rise in faecal oestrogen levels predicted egg laying. So ng playbacks by themselves induced a decrease in oestrogen levels. The re was an increase in oestrogen levels, followed by egg laying, when t he song was broadcast from inside a male model positioned away from th e nest. However, this effect occurred only when a second, silent male model was perched on the rim of the nest. If song was broadcast from i nside the model perched on the nest, there was no increase in oestroge n levels. We conclude that tests of song efficacy in female songbirds must respect some contextual rules, which are likely to vary between s pecies. Only then does it become possible to ascertain which sounds ar e most effective in inducing physiological changes leading to reproduc tion. (C) 1998 The Association for the Study of Animal Behaviour.