Meeting Abstract
Few studies have found correlations between male traits and extra-pair mating success in birds, and even fewer studies have experimentally manipulated male traits to determine if they are directly related to paternity. As a consequence, there is little evidence to support the widespread hypothesis that female birds choose attractive males as extra-pair mates. Here, we conducted an experimental study of the relationship between male plumage color and fertilization success in tree swallows (Tachycineta bicolor). The sexes are monochromatic, but frequent extra-pair mating suggests that sexual selection could be strong. Previous work suggested that male plumage brightness was positively related to male extra-pair fertilization success. In this study we experimentally dulled male plumage (with non-toxic ink markers) early in the breeding season prior to egg laying. As predicted, dulled males sired significantly fewer young (both within-pair and extra-pair) than control males. Thus, male plumage brightness is an important signal to female tree swallows choosing both within-pair and extra-pair mates.
