Intraspecific and interspecific aggression among Flame, Scarlet and Dusky Robins

Flame Petroica phoenicea and Scarlet Robins Petroica boodang are interspecifically territorial wherever they meet. However, aggressive interactions between Dusky Robins Melanodryas vittata and these two species are rare where they co-occur. Interspecific aggression among co-existing species may be due to competition for resources. In this study at Cloudy Bay, South Bruny Island, Tasmania, in August 2004-February 2005, I examined intraspecific and interspecific territoriality in Flame, Scarlet and Dusky Robins by observing displays of aggression within and between the three species. I also used song-playback experiments to test whether the robins could discriminate between conspecific and congeneric species. Flame and Scarlet Robins responded differentially to playback of each other’s song, but did not respond to Dusky Robin calls. Aggression between Flame and Scarlet Robins may be because of competition for horizontal space or resources. Conversely, the lack of aggression between Dusky Robins and these two species may be because of their ability to exploit different resources even when they are in the same area.