THE ROLE OF BRIGHT PLUMAGE IN MALE-MALE INTERACTIONS IN THE RING-NECKED PHEASANT

The brightness and colour of birds' plumages have been considered sexu ally selected traits, indicating health, condition or parasite resista nce. However, recent studies with pheasants, Phasianus colchicus, sugg est they are not signals used by females in mate choice. Instead, male s 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 differen ces in plumage brightness of the intruder. Males in the group directed more aggression to the experimentally dulled males than they did to a ny other males. This may be partly because they considered the dull ma les as novel males. When the bright and the dull males were both unkno wn, both still received more aggression than the average for any indiv idual in the group, but dull males were attacked by more males. Bright males were attacked more by the dominants and dull males by the subor dinates. The results show that plumage brightness may affect individua l 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 unisexua l groups. (C) 1997 The Association for the Study of Animal Behaviour.