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

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 (Cyanistes
cearuleus) 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.