Female Choice for Complex Song in the European Starling: A Field Experiment

Male European starlings Sturnus vulgaris sing long complex songs that appear to be important in the courtship of females but which also influence competitive interactions between males. We tested the hypothesis that females choose mates on the basis of the complexity of their songs, rather than on the quality of the territories the males defended. In order to determine whether certain territories were preferred over others, the first set of birds to settle in the experimental nest-boxes was removed and a second set allowed to settle. Consistent preferences for certain nest-boxes were indicated by correlations between the settlement patterns of the first and second sets of birds. However, males with the most complex song did not necessarily occupy the most preferred nest sites. Males with more complex song acquired mates faster. This relationship remained significant when nest-site preference was statistically controlled, indicating that female starlings chose males with complex song rather than those that defended preferred nest sites. A number of morphological variables were also found to be uncorrelated with female choice. Song complexity in European starlings increases with age, and the evolution of song complexity in this species is consistent with an age-indicator model of sexual selection. Males with larger repertoires were also in better condition, indicating that females obtain high-quality mates by choosing on the basis of male song.