FEMALE zebra finches know just how to find their ideal mate, as long as they鈥檝e heard male birdsong before. And it seems oestrogen fine-tunes their ability to pick the male singing the hardest songs 鈥� a sign he鈥檚 the fittest mate.
Zebra finches mate for life, so choosing the fittest partner is vital. Researchers know that females make their partner choice based on two factors: their early experience of male birdsong and the type of song belted out over the treetops. Until now, though, no one had looked at whether oestrogen levels influence their choice of mate, and exactly how their knowledge of birdsong affected the tunes they preferred.
Akshat Vyas at City University of New York and colleagues studied how early experience, quality of song and oestrogen levels all affected a female鈥檚 response to male birdsong.
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The team split the finches into four groups. One group had never heard male birdsong before the test, while the remaining groups were each tutored with one of three male songs: complex, simple, or long. The experiment was carried out three times, first when the finches had naturally low levels of oestrogen, because they were not ready to mate, second after artificially raising levels to mimic those normally seen prior to mating, and third, after they birds were drugged to lower oestrogen levels.
Birds tutored in long or simple songs didn鈥檛 seem to have a preference for any type of song. Untutored birds, and those primed with complex male birdsong, strongly preferred complex songs with an especially high number of unique syllables. The complex-tutored birds were even more biased towards this form of song when they had higher oestrogen levels, but their preference remained with low hormone levels. In untutored birds, raising or lowering oestrogen levels had no effect (Hormones and Behavior, ).
Both these results point to the importance of being primed with birdsong early on, say the team. 鈥淵oung females need to be exposed to songs in the same way that young ducklings need to be exposed to a mother figure,鈥� adds Jeffrey Cynx of Vassar College, Poughkeepsie, New York.
