A TASTE FOR THE BEAUTIFUL - LATENT AESTHETIC MATE PREFERENCES FOR WHITE CRESTS IN 2 SPECIES OF AUSTRALIAN GRASSFINCHES

Darwin first hypothesized that bright colors and elaborate ornamentati on of male animals evolved in response to the ''aesthetic'' mate prefe rences of females. By this reasoning, potentially costly male secondar y sexual traits may evolve not in response to selection for demonstrat ion of vigor but, rather, in response to latent, nonfunctional prefere nces by females. Recent comparative evidence for this phenomenon is eq uivocal. Here we present experimental evidence that two avian species from a lineage devoid of crested species have mate preferences for opp osite-sex conspecifics wearing artificial white crests. Other colors o f crests that have been studied are not preferred. Preferences for whi te crests did not diminish over the longest experimental interval (12 wk). These results are additional powerful evidence for highly structu red aesthetic mate preferences in estrildine finches. Sex differences in the expression of preferences, and the widespread occurrence of fac ial ornamentation in birds, suggest that the preference ''structure'' is influenced by the central nervous system. We hypothesize that aesth etic preferences are a potent force in the early evolution of sexually selected traits, and that ''indicator'' traits evolve secondarily fro m traits initially favored by aesthetic preferences.