The role of bright plumage in male–male interactions in the ring-necked pheasant

Abstract

The brightness and colour of birds’ plumages have been considered sexually selected traits, indicating health, condition or parasite resistance. However, recent studies with pheasants,Phasianus colchicussuggest they are not signals used by females in mate choice. Instead, males might rely on plumage when assessing the quality of competitors. In this study, bright and experimentally dulled males were presented to a group of captive male pheasants to determine the response to differences in plumage brightness of the intruder. Males in the group directed more aggression to the experimentally dulled males than they did to any other males. This may be partly because they considered the dull males as novel males. When the bright and the dull males were both unknown, both still received more aggression than the average for any individual in the group, but dull males were attacked by more males. Bright males were attacked more by the dominants and dull males by the subordinates. The results show that plumage brightness may affect individual recognition, but also that it is used by males to assess the quality of competitors. Male–male interactions, therefore, may have played a role in the evolution of plumage brightness, either in the context of competition for mates or for resources when males gather into unisexual groups.