Song structure and dialects in a peninsula population of the endangered Eastern Bristlebird

The elaborate, socially transmitted songs of songbirds are among the clearest examples of animal culture, and these vocalizations play key roles in reproduction and competition for resources. Failing to account for songbird vocal cultures in conservation management actions including translocation can – inadvertently – deplete cultural diversity and may negatively impact the viability of populations. However, data on vocalizations are unavailable for most cryptic and threatened songbird species, inhibiting the development of management strategies that account for and preserve important vocal cultures. We provide the first study of song for the endangered Eastern Bristlebird Dasyornis brachypterus. The Eastern Bristlebird is confined to three small, disjunct regions along Australia's east coast, and has recently undergone an ambitious three-part conservation translocation programme to minimize its risk of extinction. We recorded Eastern Bristlebird vocalizations during the breeding season preceding translocation, within the most stable and genetically diverse population, on Bherwerre Peninsula, in Jervis Bay. We quantified the species singing behaviour and song structures, and assessed geographical variation in song-sharing. Eastern Bristlebirds sang discrete 1.0-s ‘A-songs’, each comprising three to seven unique elements, within structured song bouts. Individuals had an average repertoire size of 12 different A-song types, and a total of 66 A-song types were documented across the Bherwerre Peninsula population. Song-type sharing between individuals declined with increasing geographical distance. We found evidence of dialect separation between geographically distinct groups of individuals, consistent with the spatial extent of the species' preferred coastal heathland habitat at Bherwerre Peninsula. Permuted discriminant function analysis (pDFA) showed that A-songs had a consistent internal structure, although the pDFA was better at classifying the structurally simple ‘introductory’ elements of the A-songs, than the structurally variable ‘body’ elements. Our study provides new insights into Eastern Bristlebird song culture and represents the first step towards integrating bioacoustics research into conservation management, including current and future translocations, in the hope of developing new strategies to preserve cultural diversity alongside genetic diversity in this endangered songbird species.