On the use of the acoustic evenness index to monitor biodiversity: A comment on “Rapid assessment of avian species richness and abundance using acoustic indices” by Bradfer-Lawrence et al. (2020) [Ecological Indicators, 115, 106400]

Abstract

Bradfer-Lawrence et al. (2020) have used a novel modeling approach to analyze acoustic indices, working with well-replicated data from autonomous recorders, and linking the indices to the sites’ mean avian richness rather than to simultaneous bird surveys. Their findings represent an important contribution to the literature on acoustic indices. We disagree, however, with one specific argument they make regarding the acoustic evenness index. Bradfer-Lawrence et al. (2020) argue that higher species richness should consistently lead to less even soundscapes. However, as we illustrate in this letter, using a series of examples, there are situations in which higher species richness can also lead to higher acoustic evenness.

Keywords

• Acoustic indices
• Acoustic evenness index
• Bioacoustics
• Biodiversity monitoring
• Soundscape ecology