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Vocal instability over time in individual male European nightjars, Caprimulgus europaeus: recommendations for acoustic monitoring and surveys

Raymond, Sarah; Spotswood, Sarah; Clarke, Hazel; Zielonka, Natalia; Lowe, Andrew; Durrant, Kate L

Authors

Sarah Raymond

Sarah Spotswood

Hazel Clarke

Natalia Zielonka

Andrew Lowe



Abstract

Acoustic monitoring of birds is developing rapidly as equipment, methods and analyses improve. However, most population monitoring studies still utilise traditional techniques like mark-recapture or line transects. Rebbeck et al. (2001) used vocal recordings of male European nightjars, Caprimulgus europaeus, to identify individuals, finding that four acoustic parameters correctly assigned 98.5% of calls to individuals. We tested Rebbeck et al.’s methods on a population of European nightjars recorded over two successive breeding seasons and found that percentage of males correctly classified within a season reached a maximum of 73.5%, rising to 75% if full-length calls and 13 acoustic parameters were used. We tested whether males could be re-identified over a two-year period and found that only 20% of calls were assigned to the same putative territorial individuals, despite separate ringing data showing that males can maintain site fidelity for up to eight years. Our results indicate that the characteristics of male nightjar vocalisations may alter over time. We therefore recommend that vocal discrimination be used in conjunction with existing monitoring techniques when surveying for population monitoring, that as many call parameters as possible are used and that recording for automated presence/absence surveys takes place over a short time-frame.

Citation

Raymond, S., Spotswood, S., Clarke, H., Zielonka, N., Lowe, A., & Durrant, K. L. (2020). Vocal instability over time in individual male European nightjars, Caprimulgus europaeus: recommendations for acoustic monitoring and surveys. Bioacoustics, 29(3), 280-295. https://doi.org/10.1080/09524622.2019.1603121

Journal Article Type Article
Acceptance Date Mar 3, 2019
Online Publication Date Apr 19, 2019
Publication Date 2020
Deposit Date Apr 5, 2019
Publicly Available Date Mar 28, 2024
Journal Bioacoustics
Print ISSN 0952-4622
Electronic ISSN 2165-0586
Publisher Taylor and Francis
Peer Reviewed Peer Reviewed
Volume 29
Issue 3
Pages 280-295
DOI https://doi.org/10.1080/09524622.2019.1603121
Keywords European nightjar, caprimulgus europaeus, acoustic monitoring, vocal individuality, census method, discriminant function analysis
Public URL https://nottingham-repository.worktribe.com/output/1752016
Publisher URL https://www.tandfonline.com/doi/abs/10.1080/09524622.2019.1603121?journalCode=tbio20
Additional Information This is an Accepted Manuscript of an article published by Taylor & Francis in Bioacoustics on 19/04/2019, available online: http://www.tandfonline.com/10.1080/09524622.2019.1603121.

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