Male and female birds often participate differently in nest building, egg incubating, and chick feeding and a recent study sought to better understand these differences. Reviewing the habits of over 1,500 species, they found that solo female parenting was more common when there was strong sexual selection on males (females are choosy when they do all the work) and when male paternity was less certain (males don't help if it might be another individual's offspring). Predation risk, clutch size and nestling development did not affect parental participation.
The researchers found that parenting roles often change during the breeding season. For most species (938), both parents participated in nest building, but incubation was conducted exclusively by the females in more species (768) than by both parents (740). When the time came to feed chicks, both parents contributed in the majority of species (1344).