Exploring the application potential of ecoacoustic indices as a rapid assessment tool of avian species richness in southeastern pine forests

The efficacy of using ecoacoustic indices as a rapid assessment tool of the avian community has yet to be studied in southeastern pine forests. Here we use a passive recording method and information theoretic approach to explore whether the Acoustic Complexity Index (ACI) and Normalized Difference Soundscape Index (NDSI) vary in relation to avian species richness and factors considered to influence species richness. We also examine how patterns change depending on time-scale (seasonal average per hour versus seasonal average) and test whether these indices vary in relation to species connectedness of a site. Seasonal average ACI and NDSI did not change significantly with management actions (i.e., supplemental feeding, snag retention and prescribed burn recency), though management actions were included in the best-supported models. Anthrophony was included in the best models regardless of time-scale for both ACI and NDSI and had a significant, nonlinear effect on hourly average ACI depending on season. In general, there were nuanced differences in how ACI and NDSI related to factors thought to influence species richness, and the relationship to these variables depended on the timescale of analysis. Neither ACI nor NDSI related to the cooccurrence of indicator species or breeding season avian species richness. However, we found NDSI to be most consistent among highly connected recording sites that share many species with many of the other recording sites. Our results provide new insights into the application potential of ecoacoustic indices in southeastern pine forests. • Acoustic complexity index varies with season and anthrophony. • Time-scale of analysis revealed inconsistencies in these relationships. • Indices were not related to indicator species or breeding season species richness. • NDSI is most consistent among sites that share many species with many other sites.