Sex differences in parental care in the common swift (Apus apus): effect of brood size and nestling age

We analysed sex differences in parental behaviour in a Mediterranean population of common swifts (Apus apus). Females attended the nest and fed the chicks at a higher rate than males and were more in contact with the nestlings during the first days after hatching, while no sex differences were found in other parameters measured. For larger broods no quantitative sex differences were observed in meal-delivery and brooding time, while for small broods the rate of feeding by males was lower than the rate of feeding by females, and males attended the nest less than females. No sex differences were observed at the early nestling stage, but males attended the nest less than females later in the nestling stage. No extra-pair breeding activity was observed. These results suggest that males reduce parental care when the energy requirements of the chicks decrease, while females do not.