Predictors of reproductive success in dark-eyed juncos (Junco hyemalis)

Abstract

According to the theory of sexual selection, sexual traits are linked with reproductive success. Bird song is a male sexual trait that can communicate aspects of the signaler's quality to prospective mates and potential rivals, and signal traits that are physically challenging to produce can enforce signal honesty. These phenotypic traits, along with nest habitat characteristics and weather variables, have been shown to influence the reproductive success of birds. In the current study, I tested whether these variables are associated with reproductive success in dark-eyed juncos (Junco hyemalis). I found no evidence that song traits are challenging to produce, and average reproductive success per nesting attempt was not related to any measure of song structure or body size. Hatching success was significantly higher when canopy cover and average daily precipitation were lower and tended to be higher in nests with better insulation and at sites with lower stem density. Fledging success was not significantly associated with any microhabitat or weather variables, but it tended to increase with low nest exposure. The findings of this study suggest that the reproductive success of these ground-nesting songbirds depends more on nest habitat characteristics and temperature during the nesting period than on male phenotypic traits.