Male decisions or female accessibility? Spatiotemporal patterns of extra pair paternity in a songbird

Extra pair paternity is widespread in birds, but its high variability across years, populations, and species is to a great extent unresolved. Here we explored, during 2 breeding seasons, population and individual accessibility to fertile females at different spatiotemporal scales in a population of pied flycatchers (Ficedula hypoleuca) to understand whether individual patterns of extra pair paternity were due to adaptive individual behavior or ecological constraints. Our aim was to comprehend variation in extra pair paternity population patterns through the understanding of individual behavior. At the population level, extra pair paternity probability decayed with distance between nests. At the individual level, however, males engaged in extra pair paternity with distant (up to 390 m) females despite the fact that there were often fertile females in closer territories. Extra pair paternity cases occurred mostly during egg laying and the incubation of the extra pair male’s social female despite that other neighboring females were fertile before and after these periods. Results suggest a male strategy to maximize reproductive output by guarding their social females during their peak of fertility, seeking extra pair paternity afterwards and investing in parental duties once their social nestlings hatch. This may explain why extra pair paternity rate was higher in the year with lower breeding synchrony, because this allowed early-breeding males to have more extra pair paternity opportunities after their social mate laying onset. This study highlights the necessity of considering the social contexts of individuals at the spatiotemporal scales at which extra pair paternity takes place to understand variation in extra pair paternity patterns at the individual and population levels.