Bioacoustics of Cinnyris

Our results indicate that the olive-backed sunbird represents a superspecies and should be split into at least four species (Supporting Information, Table S10). We have found support for the three-way split suggested by Eaton etal. (2021) while also providing the first genetic, acoustic and morphological evidence that the ‘Wakatobi sunbird’ warrants recognition as a full species. The Wakatobi population exhibits a strikingly non-linear arrangement of population structure, with a range enveloped within that of the more widespread species, and had previously been suggested as a ‘limbo split’ ( Rheindt, 2021 ) based on plumage differences alone ( Eaton et al. , 2021 ). Our study has supported these differences with matching patterns in mtDNA and integrative species delimitation or ‘Tobias scoring’ ( Tobias et al. , 2010 ). Due to the lower effective population size of mtDNA, along with other factors, differences in mtDNA should be integrated with other forms of evidence in this way ( Rubinoff & Holland, 2005 ). In the light of this new integrative evidence, we recommend that the ‘Wakatobi sunbird Cinnyris infrenatus ’, originally named by Hartert (1903) , be reinstated as a separate species. In addition to its genetic divergence ( Fig. 3 ), the ‘Wakatobi sunbird’ has shorter wings, a shorter bill and longer tarsi than the ‘Sahul sunbird’ (Supporting Information, Fig. S9), as well as exhibiting slower and higher pitched calls over a smaller bandwidth (Supporting Information, Fig. S11). This study is one of several to have remarked upon the distinctness of the Wakatobi avifauna ( Kelly et al. , 2014 ; O’Connell et al. , 2019a , c), and so we reiterate the recommendation of O’Connell et al. (2020) that the Wakatobi Islands should be protected as an Endemic Bird Area ( Stattersfield et al. , 1998 ).