Sexual Selection

The study of sexual selection is concerned with the evolution of characters involved in competition for mates. Several studies have provided conclusive evidence that females prefer more conspicuously ornamented males. Females paired with attractive partners may gain direct benefits, such as territorial resources and parental care, or indirect benefits, such as more viable offspring, as suggested by the good genes process, or more attractive offspring, as suggested by the Fisher process. We study the reed bunting (Emberiza schoeniclus) to assess male characteristics involved in female (extra-pair) choice and subsequent fitness consequences. Females preferred males with larger breast badges which is an indicator for male age. Furthermore, controlling for maternal effects, young sired by males with larger breast badges were in better condition than young sired by males with small badges (supporting ‘good genes model’) .

In several species females also show some expression of the same ornaments as males. Female ornaments may be correlated effects of selection on males or may have a signalling function in their own right. We investigate the reproductive correlates of throat feather ornaments in both sexes of the European starling (Sturnus vulgaris). Both sexes possess iridescent throat feathers, which are actively displayed during courtship by males. Our results suggest that throat feather ornaments could be favoured by mutual sexual selection and may have a signalling function in both sexes. These feathers provide reliable information on age and, perhaps as a result or perhaps in addition, individual quality. However, we do not know if that information is actually used; other cues could be more important. Furthermore, the proximate benefits of mating with an older ornamented partner appear to differ between the sexes. Our tentative conclusion sets the stage for several interesting hypotheses to be tested in future manipulative experiments.