Data from: Ecological and social factors constrain spatial and temporal opportunities for mating in a migratory songbird

Many studies of sexual selection assume that individuals have equal mating opportunities and that differences in mating success result from variation in sexual traits. However, the inability of sexual traits to explain variation in male mating success suggests that other factors moderate the strength of sexual selection. Extra-pair paternity is common in vertebrates and can contribute to variation in mating success, and thus serves as a model for understanding the operation of sexual selection. We developed a spatially explicit, multi-factor model of all possible female-male pairings to test the hypothesis that ecological (food availability) and social (breeding density, breeding distance, and the social mate's nest stage) factors influence an individual's opportunity for extra-pair paternity in a socially monogamous bird, the black-throated blue warbler, Setophaga caerulescens. A male's probability of siring extra-pair young decreased with increasing distance to females, breeding density, and food availability. Males on food-poor territories were more likely to sire extra-pair young, and these offspring were produced further from the male's territory, relative to males on food-abundant territories. Moreover, males sired extra-pair young mostly during their social mates' incubation stage, especially males on food-abundant territories. This study demonstrates how ecological and social conditions constrain the spatial and temporal opportunities for extra-pair paternity that affect variation in mating success and the strength of sexual selection in socially monogamous species.