Sex differences in parental response to offspring begging are associated with pair bond strength across birds

Abstract

Mothers, fathers, and offspring regularly clash over how much care offspring receive. Offspring beg to solicit for more resources--but how much begging is rewarded can depend on who is listening. While both parents benefit from provisioning offspring, each would benefit from their partner shouldering more of the burden of care, leading to sexual conflict. Additionally, if the costs and benefits of provisioning differ by sex, parent-offspring conflict should vary by sex. How these evolutionary conflicts influence sex differences in parent-offspring communication is unknown. To determine whether the sexes differ in their response to offspring signals, we conducted a meta-analysis on 30 bird species, comparing responsiveness to social and physiological traits affecting conflict. We found that a species' typical pair bond strength predicts whether males or females respond more to offspring begging. In species with stable and/or monogamous bonds, and thus lower sexual and paternal-offspring conflict, males' provisioning effort is more strongly correlated with offspring begging than females'. The opposite holds for species with weak pair bonds: females respond more to begging, perhaps compensating for males' lower responsiveness. These results demonstrate that sex differences in parental care can arise via sex differences in parent-offspring communication, driven by evolutionary conflicts.