Male incubation feeding in songbirds responds differently to nest predation risk across hemispheres

Evolution of parental care behaviour has been of considerable interest to behavioural ecologists for a long time. Incubation feeding, where an individual incubating eggs is provisioned by another individual, is an important component of avian parental care. It may be critical for breeding success by allowing the incubating bird to spend more time on the eggs. However, very little is known about environmental factors shaping incubation feeding, and incubation behaviour in general, of tropical and southern hemisphere birds, and how this differs compared to northern hemisphere species. We collated available data on the rate of incubation feeding in Australian, New Zealand and North American songbirds (78 species from 25 families). There was a strong positive relationship between female incubation attentiveness and incubation feeding by males; however, female attentiveness was higher in North America than in Australia and New Zealand for the same intensity of male incubation feeding. Incubation feeding was not related to species body mass, social organization, geographical latitude or ambient temperature. It differed significantly between families, but overall was not different between regions. Incubation feeding rate was related to nest predation rate, but differently in the two regions. It increased with nest predation rate in Australia and New Zealand, but decreased with nest predation rate in North America. We suggest that this may be caused by different predator-prey interactions in North America versus Australia and New Zealand, which could have shaped the evolution of incubation feeding differently.