Fashion and age in pheasants: age differences in mate choice

Abstract

Commonly, younger males have less exaggerated secondary sexual characters than older males. In recent models of the evolution of ornamental traits through intersexual selection, it is often assumed that the ornaments confer a handicap to the bearers and thus reflect males9 phenotypic condition. Hence, if younger males have a lower cost in growing their less exaggerated ornaments because of delayed development, it could be expected that those traits should be less revealing of condition in younger individuals. Consequently, in species where the development of ornaments is age dependent, females should pay less attention to condition-dependent traits when choosing among younger as compared with older males. This study on ring-necked pheasants shows that males9 attraction of females, measured in the wild by radio-tracking, was less affected by spur length in 1-year-old males than in older males. In addition, analysis of fluctuating asymmetry suggests that the shorter spurs of 1-year-old pheasants were less revealing of male quality.