Songs of the Red-capped Robin, Petroica goodenovii: comparison of acoustic features in island and mainland populations

Abstract

We studied the songs and singing behavior of Red-capped Robins (Petroica goodenovii) on Rottnest Island and in mainland Dryandra Woodland State Forest, Western Australia. We compared the song structure and acoustic features of the 'tinkle' and 'blurt' vocalisations in those two locations, and in addition we examined songs of Red-capped Robins recorded in eastern Australia. We found that the tinkle songs of the birds of Rottnest Island differed in the temporal pattern of note phrases from those at Dryandra, and detailed analyses revealed that the acoustic features of the notes constituting tinkle songs were significantly different as well. Linking together of two or more songs was common in the singing behavior of Dryandra birds but unusual in Rottnest Island birds. Tinkle songs from Eastern Australia were similar to those of Dryandra, suggesting widespread uniformity of the tinkle song on the mainland, and emphasising the differentiation of the Rottnest Island form of the tinkle song. In contrast to the results on tinkle songs, the blurt songs of the island and all mainland birds differed very little, suggesting different developmental processes for the two song forms.