The impact of vehicular noise on acoustic indices within simulated bird assemblage soundscapes

ABSTRACT

Passive acoustic monitoring (PAM) is a sampling technique that has gained increasing popularity in the field of wildlife monitoring and research since it allows for non-invasive and cost-effective collection of acoustic information. Retrieving biological information from PAM recordings can often involve time-consuming sound annotation methodologies, but the advent of acoustic indices can help expedite this process. While correlations between acoustic indices and species richness have been observed in a variety of ecological contexts, these relationships faulter in environments with increased vehicular noise. Here, we assessed the direct impact of vehicular noise on nine acoustic indices through controlled manipulation of vehicular noise within computer-generated bird assemblage soundscapes. Our results demonstrate that recording distance from roadsides and number of passing cars per minute have notable and persistent impacts on acoustic index values, but the magnitude of the effect varies across indices. Four acoustic indices demonstrated greater resilience to vehicular noise interference and may therefore be better suited for developed areas: Bioacoustic Index, Acoustic Complexity Index, Acoustic Diversity Index, and Acoustic Evenness Index. By contributing to the collective understanding of acoustic index behaviours under anthropogenic noise pollution, we hope to better inform their ecological application in human-developed contexts.

KEYWORDS:

• Acoustic indices
• anthrophony
• avian monitoring
• passive acoustic monitoring
• soundscapes
• vehicular noise

Acknowledgements

For assistance and discussions, we thank Guillaume Bastille-Rousseau, Christopher L. Butler, Shasta S. Corvus, Elaine M. Metz, Clayton K. Nielson, the 2022 Sounds of Nature Citizen Science Project volunteers, and the journal’s editors and referees. Funding was provided by the McIntire-Stennis Formula Grant through the National Institute of Food and Agriculture. The funders had no role in the design, analysis, decision to publish, or preparation of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/09524622.2024.2332748.

Author contributions

RLD and BSP conceived the ideas and designed methodologies; RLD created the soundscapes, collected and analyzed data, and led the writing of the manuscript. BSP provided funding, analyzed data, and provided critical revisions for manuscript drafts. Both authors gave final approval for publication.

Data availability statement

Data and code are available through the Dryad Digital Repository https://doi.org/10.5061/dryad.sxksn038p.

Additional information

Funding

This work was supported by the McIntire-Stennis Formula Grant from the National Institute of Food and Agriculture.