Interspecific Aggression and Territorial Behavior Between Scarlet Robin Petroica multicolor and Flame Robin P. phoenicea

Abstract

Scarlet Robins and Flame Robins defended mutually exclusive temtories against one another at a site in south-eastem New South Wales. Playback experiments indicated that each species distinguished the song of the other species from a control species' song. Playback experiments further showed that each species responded most intensely to playback of conspecific song, less intensely to playback of the other robin species' song and hardly at all to the control species' song. When Flame Robins first arrived at the study site from their wintering grounds they were initially dominant to Scarlet Robins and established territories within Scarlet Robins' winter temtories. Once interspecific territory boundaries had been established, the outcome of disputes was decided by the ownership status of contestants rather than species' status. Interspecific territoriality between Scarlet and Flame Robins may be a recent phenomenon resulting from changes to the forest environment such that both species have come into contact. One or other species may also have expanded its range in recent years. Interspecific aggression was perhaps stimulated initially by mistaken identification of sympatric species of robin, but now appears to continue because of interspecific competition for food and foraging space. It is envisaged that interspecific territorial behaviour will occur wherever Scarlet and Flame Robins come into contact during their breeding seasons.