Temperature variability is associated with the occurrence of extra-pair paternity in blue tits

<p>In birds, extra-pair 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 blue tit (<em>Cyanistes</em> <em>cearuleus</em>) we assess the importance of ambient temperature in modulating the levels of extra-pair paternity. Here, we show that variability of local thermal conditions affects the occurrence of EPP. Specifically, we found that the probability of EPP increased with increasing variability in ambient temperature experienced by females prior to egg laying. This pattern is consistent with the idea of plastic female responses to unpredictable environmental conditions. Our results suggest that extra-pair mating may represent an adaptive behavioural strategy to compensate for possible negative effects of unpredictable environmental conditions. </p>