Habitat use and foraging behaviour of the scarlet robin and the flame robin at a site of breeding-season sympatry

Abstract

The habitat selection and foraging ecology of scarlet robins (Petroica multicolor) and flame robins (Petroica phoenicea) were observed for three years at a site of breeding-season sympatry in order to examine seasonal patterns of foraging behaviour, habitat and resource use, and the significance of competition for food as a cause of interspecific aggression. Both species occupied habitats with open ground layers of grass or bark, and a sparse shrub-and-sapling layer. Flame robins occupied more mesic habitats; scarlet robins occurred in drier habitats. Seven habitat variables provided 73% separation between habitats occupied by the two species of robin. Both species foraged mostly on the ground during the cooler months. In summer and autumn, scarlet robins became snatchers of arthropods from bark and foliage substrates, and flame robins hawked for flying insects close to the ground. High overlap between their use of available foraging space, especially vertical foraging space, probably caused interspecific competition for food and space, leading to interspecific aggression and territorial behaviour. Such competition, in conjunction with the flame robin's interspecific dominance and apparently greater resilience to practices such as timber harvesting, may cause long-term changes to the distribution and relative abundance of each species. Recommendations for habitat management are considered briefly.