The researchers played recordings of attractive songs and less attractive control songs of male canaries to female domesticated canaries. When the females started egg-laying they varied the size of their eggs in the nest according to the attractiveness of the male’s song; the more attractive the song, the larger the eggs.

However the researchers from the University of London and Germany’s Max Planck Institute for Ornithology showed that while larger eggs were more likely to contain male offspring in natural environments, in the experiment there was no difference in brood sex ratio between the different songs played to the females. The researchers say that suggests different levels of female control.

Male birdsong has long been known to attract females and influence mate choice decisions and even induce an alteration in the offspring’s sex ratio. This study shows experimentally that hearing an attractive song also has a selective impact on female physiology.

The study is published in the current issue of the journal Ethology.