Pairs of zebra finches with similar ‘personalities’ make better parents

Although behavioural plasticity should be an advantage in a varying world, there is increasing evidence for widespread stable individual differences in the behaviour of animals: that is, ‘personality’. Here we provide evidence suggesting that sexual selection is an important factor in the evolution of personality in species with biparental care. We carried out a cross-fostering breeding experiment on zebra finches, Taeniopygia guttata, and found that parental personality traits and the combination of personalities within breeding pairs had positive effects on correlates of (foster) offspring fitness (body mass and condition). Furthermore, these nongenetic parental effects were pervasive and carried over into the next generation. Our results suggest that similarity in behavioural traits of biparental species can have important, long-lasting effects on reproductive success, probably because of reduced sexual conflict over the provision of parental investment.