Access to Winter Food Resources by Bright- versus Dull-Colored House Finches

The adaptive significance of delayed plumage maturation in passerines is not yet understood, despite much discussion and speculation (Selander 1965; Rohwer 1975, 1978; Rohwer and Niles 1979; Rohwer et al. 1980; Flood 1984; Studd and Robertson 1985; Lyon and Montgomerie 1986). Rohwer (1986) recently suggested that female-like subadult plumages may confer competitive advantages to yearlings during the winter, when individuals compete for access to critical food resources. Virtually all empirical study of delayed plumage maturation in birds to date has been done during the breeding season, and there is little evidence to evaluate Rohwer's hypothesis that female-like plumages benefit individuals during the nonbreeding season. In this paper we report that female-like plumage in House Finches (Carpodacus mexicanus) is potentially advantageous during the winter, when males yield access to critical food resources in favor of females.