Digest: Extra-pair mating and inbreeding avoidance in a socially monogamous fairy-wren.

Infidelity in socially monogamous birds may be a mechanism of inbreeding avoidance and may be impacted by cooperative breeding. Hajduk et al. (2018) find that relatedness increases extra-pair mating only in mother-son social pairs of Malurus cyaneus, while a greater number of nest helpers consistently increases the proportion of extra-pair offspring. These findings suggest that there may be multiple explanations for extra-pair mating within a single population.