Vocal signals of ontogeny and fledging in nestling black-cockatoos: Implications for monitoring

ABSTRACT

Bioacoustics offers new ways to monitor wildlife populations. Understanding vocal changes related to age can provide demographic data that are valuable but difficult to collect for threatened species. Here, we present the vocal signals of ontogeny and fledging in nestlings for two endangered black-cockatoos, the Kangaroo Island glossy black-cockatoo, Calyptorhynchus lathami halmaturinus, and the south-eastern red-tailed black-cockatoo, C. banksii graptogyne. Using sound recordings taken at wild nests (n = 3 for the red-tailed black-cockatoo; n = 7 for the glossy black-cockatoo), we examined changes in nestling vocalisations through to fledging. Nestlings vocalised from 4 weeks of age, but calls were soft and infrequent until about 6 weeks. Daily call rate increased significantly in the final week of nesting. Peak amplitude increased significantly with development for both subspecies. Call duration increased significantly for the glossy black-cockatoo. Likewise, low frequency increased significantly for the glossy black-cockatoo. Average entropy decreased significantly for both subspecies. Aggregate entropy decreased significantly for the red-tailed black-cockatoo. Fledging was associated with a loud and distinct vocal event. Together, these changes in call rate and structure, and the presence or absence of fledging vocalisations, provide useful ways to broadly categorise nest age and determine nest outcome from sound recordings.

KEYWORDS:

• Ontogeny
• fledging
• bioacoustics
• black-cockatoo
• vocalisations
• monitoring

Acknowledgements

For help in the field, we thank Tim Burnard and Evan Roberts from the south-eastern red-tailed recovery team and Karleah Berris and Torran Welz from the Kangaroo Island glossy black-cockatoo recovery programme. We thank the landowners who allowed this research on their properties. We thank the members of the Ecosounds Lab at the Queensland University of Technology for help with sound data handling and storage. We thank Dr. Simone Blomberg from The University of Queensland for statistical help. This project was supported by an Australian Postgraduate Award, the National Environmental Science Programme’s Threatened Species Recovery Hub and the Glossy Black Conservancy.

Ethical statement

This work was conducted under animal ethics approval number SBS/076/17/VIC and SBS/DEWNR/219/17 issued by The University of Queensland Animal Ethics Committee.

Disclosure of potential conflicts of interest

There are no known conflicts of interest.

Data availability statement

The data that support the findings of this study are available from the corresponding author, Daniella Teixeira, upon reasonable request.

Additional information

Funding

This work was supported by an Australian Postgraduate Award (Australian Government), the National Environmental Science Programme’s Threatened Species Recovery Hub (Australian Government) and the Glossy Black Conservancy.