BADGE SIZE IN COLLARED FLYCATCHERS PREDICTS OUTCOME OF MALE COMPETITION OVER TERRITORIES

The evolution of conspicuous coloration is often hypothesized to be dr iven by sexual selection, where colour traits may function as honest s ignals of individual abilities in male contest competition and female choice. However, game theory models suggest that colourful badges (i.e . energetically cheap signals) may have no function in sexually select ed contests, because the value of the contested resource is too high r elative to the costs of fighting. We investigated this assertion by ex perimentally staging male contests over nest sites (a crucial resource for attracting females) in old (greater than or equal to 2 years) mal e collared flycatchers, Ficedula albicollis. Males with a relatively l arge white forehead patch (i.e. a condition-dependent plumage trait di splayed in male contests) enjoyed a competitive advantage in disputes over experimentally vacated territories. No other measured morphologic al variable predicted the outcome of such a dispute. Furthermore, the winners of the disputes acquired a female more quickly than did the lo sers. Thus, our results suggest that the white forehead patch of male collared flycatchers may function as a badge of status that is also us ed in sexually selected contests over resources. We suggest that this is because the value of the contested territory may be relatively low compared with the cost of fighting when alternative vacant sites exist in the neighbourhood. (C) 1997 The Association for the Study of Anima l Behaviour.