Bioacoustic correlates of female choice in European starlings

Abstract

The elaborate structure of male European starling song suggests that it is a trait under heavy sexual selection pressures, and the results of several studies in both the laboratory and the field have identified song as the only male characteristic correlated with female choice in this species. However, previous studies have failed to isolate the bioacoustic feature(s) of song that are important for mating decisions and preferences in female starlings. An operant apparatus that reinforces a natural approach response to potential nest sites with different male starling songs is used to demonstrate that female preference is positively correlated with song bout length but not repertoire size (two features that normally covary). Further, this preference for longer song bouts is made in such a way that the absolute length of a bout cannot be the feature upon which the preference is based. A method for quantifying the temporal structure and stereotypy in male starling songs is presented using information theory, and it is shown that these measures correlate very closely with different song bout lengths. The importance of song bout stereotypy for female preference is then tested using synthetic stimuli or operant apparatus.