Male mate preference against tail-elongated females in the barn swallow

Abstract

AbstractThe function of female ornamentation in the context of (inter)sexual selection attracts keen attention these days, but empirical field studies are mostly based on indirect measures such as mating patterns; direct evidence of male mate preference on female ornamentation while controlling for confounding factors is needed. Here we performed model presentation experiments to study male mate preference in the barn swallow Hirundo rustica, a model species of sexual selection. Female barn swallows have somewhat shorter tails than males, but their tails are still long and costly. Although many correlational and experimental studies of live females have focused on long tails in female barn swallows over the last three decades, direct behavioral tests of male mate preference are lacking. By using a sequential model presentation experiment, in which we repeated the trials with the same males, we found that males significantly reduced the number of pairing displays when they were presented with tail-elongated female models compared to control female models. Interaction between treatment and male tail length was far from significant. The observed pattern is inconsistent with the prevailing view that costly female ornamentation is maintained via male preference for more ornamented females. Rather, the observed pattern is consistent with the sexual mimicry hypothesis, in which females can avoid sexual (and social) harassment by mimicking males.