Developing a passive acoustic monitoring technique for Australia’s most numerous seabird, the Short-tailed Shearwater (Ardenna tenuirostris)

ABSTRACT

Establishing appropriate conservation management objectives and actions for seabirds requires timely detection of changes in their populations. However, obtaining regular accurate measures of seabird population size and trends can be difficult due to logistical and financial constraints in accessing remote breeding sites. The Short-tailed Shearwater (Ardenna tenuirostris) is a wide-ranging, burrow-nesting Procellariiform with an estimated breeding population size of ca 23 million individuals. Despite its ecological significance, there is currently limited monitoring of the species. In the present study, eight acoustic data loggers were deployed across six sites over two breeding seasons to assess the efficacy of acoustic monitoring. Five acoustic indices were used to investigate vocal activity over the breeding season, detect phenology events, and to determine the most accurate period to assess the density of occupied nests. The general pattern over the breeding season was similar for several of the acoustic indices and reflected colony attendance patterns. Linear regressions fitted to the normalised difference soundscape index values and density of occupied nests (burrows·m⁻²) revealed significant relationships in both the incubation and chick-rearing. The results suggest that passive acoustic monitoring could be used as an effective method to predict nesting density in Short-tailed Shearwater breeding colonies. Used in conjunction with information on the breeding colony area, this could enable regular estimates of colony population size. Such information is crucial for the early detection of population trajectory changes. The method may also be applicable for other burrow- or surface-nesting seabirds for which regular wide-spread monitoring currently proves difficult.

KEYWORDS:

• Bioacoustics
• monitoring
• Ardenna tenuirostris
• burrow-nesting seabird
• acoustic indices
• Short-tailed Shearwater

Acknowledgements

We are grateful to the many field assistants who were involved with data collection for this study, in particular, Melanie R. Wells and Timothée Poupart. We thank Parks Victoria for logistical support and are especially grateful to Phil Reichelt, Leo Op Den Brouw, Geoff Sharpe and Tony Symes. We thank Desley Whisson for advice on acoustic data analysis. We also thank the anonymous reviewers for providing helpful comments on the manuscript. The Institut Universitaire de France (IUF) is acknowledged for its support to PB as a Senior Member.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics statement

Research was conducted following the ethical guidelines of the Deakin University Animal Ethics Committee (Approval B30-2016) under the Department of Environmental, Land, Water and Planning (Victoria, Australia) Wildlife Research Permit #10008043 and the Department of Primary Industries, Parks, Water and Environment (Tasmania, Australia) Wildlife (General) Regulations 2010 (Regulation 24 and 25) and Threatened Species Protection Regulation 2006 (Regulation 4).

Supplementary Material

Supplemental data for this article can be accessed here.

Additional information

Funding

This project was financially supported by research grants from The Holsworth Wildlife Research Endowment and The Ecological Society of Australia, The Winifred Violet Scott Charitable Trust, and Sea World Research & Rescue Foundation.