Re-assessing species limits in a morphologically cryptic Australasian kingfisher lineage (Coraciiformes: Halcyonidae) using bioacoustic data

Abstract The common paradise-kingfisher, Tanysiptera galatea, species complex comprises 19 taxa distributed across New Guinea and Wallacea. Owing to its highly conserved morphological features, the lineage has been taxonomically confused, with 15 similar-plumaged taxa currently treated as conspecific. To shed light on species limits, we analysed eight bioacoustic parameters across 107 sound recordings using principal component analysis and the Isler criterion, among other methods. Our results show that multiple geographical entities of Tanysiptera paradise-kingfishers form discrete bioacoustic clusters across several vocal parameters, suggesting that species diversity of the common paradise-kingfisher complex has been greatly underestimated. Based on our results, we propose splitting T. galatea into six species: (1) Obi paradise-kingfisher, Tanysiptera obiensis; (2) Rossel paradise-kingfisher, Tanysiptera rosseliana; (3) Papuan paradise-kingfisher, T. galatea; (4) Halmahera paradise-kingfisher, Tanysiptera margarethae; (5) Morotai paradise-kingfisher, Tanysiptera doris; and (6) Amboyna paradise-kingfisher, Tanysiptera nais. Our work highlights that the non-invasive collection of avian vocal data is a crucial taxonomic tool and adds to increasing evidence that bioacoustic analyses are effective in elucidating cryptic diversity.