Habitat Partitioning and Interspecific Territoriality in Flame, Scarlet and Ducky Robins

Flame (Petroica phoenicea), Scarlet (P. boodang) and Dusky (Melanodryas vittata) Robins occasionally occur sympatrically in Tasmania. All three species are insectivorous, inhabit forests with an open understorey, and are ecologically similar. The question then arises as to how they are able to coexist. In this study, foraging behaviour, habitat selection and interspecific territoriality in the three species were examined. Flame and Scarlet Robins are known to be interspecifically territorial. We predicted that this is due to similarities in their use of resources, such that they cannot coexist in the same area. The Dusky Robin may be able to exploit different resources from Flame and Scarlet Robins, negating the need for territoriality between Dusky Robins and the other two species. Surprisingly, Scarlet Robins were more similar to Dusky Robins in their resource use than they were to Flame Robins, even though Flame and Scarlet Robins are congenerics. Although this should prevent Dusky Robins from sharing territories with Scarlet Robins, they actually had a greater territory overlap with Flame and Scarlet Robins, than these species had with each other. We suggest that Scarlet Robins compensate for the overlap by Dusky Robins by traversing a larger area in order to obtain sufficient resources.

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