Temperature variability is associated with the occurrence of extrapair paternity in blue tits

In birds, extrapair paternity (EPP) constitutes an alternative mating strategy, with potentially important fitness consequences for both males and females and their offspring. Several factors have been identified that can influence the occurrence of EPP, but the role of environmental variability has so far received relatively little attention. Using long-term data set from a wild population of the blue tit (Cyanistes cearuleus), we assess the importance of ambient temperature in modulating the levels of extrapair paternity. Here, we showed that the variability of local thermal conditions affects the occurrence of EPP. Specifically, we found that the probability of EPP increased with rising variability in ambient temperature experienced by females prior to egg laying. This pattern is consistent with an idea of plastic female responses to unpredictable environments. Our results suggest that extrapair mating may represent an adaptive behavioral strategy to compensate for the potential negative effects of unstable environmental conditions.