Faithful females receive more help: the extent of male parental care during incubation in relation to extra-pair paternity in songbirds

Parental care provided by males occurs in a diverse array of animals and there are large differences among species in its extent compared to female care. However, social and ecological factors responsible for interspecific differences in male’s share of parental duties remain unclear. Genetic fidelity of females has been long considered important. Theory predicts that females should receive more help from their mates in raising the offspring in species with high genetic fidelity. Using avian incubation behavior as a model system, we confirmed this prediction. The extent of male’s help during incubation increased with decreasing rate of extra-pair paternity across species (22 species of socially monogamous songbirds from 13 families; male’s share of incubation ranged from 6% to 58%), even after accounting for covariates, biases in species selection and intraspecific variability. Moreover, this result was not sensitive to two different phylogenies and branch length estimates. We suggest t...