Data for: Investigating the Effects of Tree Species Diversity and Relative Density on Bird Species Richness with Acoustic Indices

Description

Mixed-species forest stands may provide suitable habitats for a greater number of bird species than tree monocultures by increasing the number of niches and resources available. However, assessing the effects of forest diversity on birds over time and across multiple sites using traditional survey methods can be expensive, time-consuming and impractical. We used passive acoustic monitoring (PAM) and acoustic indices to investigate how tree species diversity, relative density, and other plot characteristics affect the species richness of avian communities in temperate forests. Acoustic surveys were conducted in the Hainich National Park, Germany, using plots which differed in tree species diversity and relative species density. Of the five acoustic indices assessed, the normalised difference soundscape index (NDSI), the acoustic complexity index (ACI) and bioacoustic index (BI) performed best in separating biophony from other soundscape elements whereas the acoustic evenness index (AEI) and temporal entropy (Ht) were biased towards geophony, anthrophony and silence. NDSI, ACI and BI displayed significant positive relationships with bird species richness but NDSI plateaued at 5 bird species. Plot tree species diversity had significant positive effects on ACI and BI during dawn, dusk and daytime periods. Increased basal area of sycamore (Acer pseudoplatanus) and, to a lesser degree, beech (Fagus sylvatica), had a negative effect on acoustic indices. These results could potentially be due to the earlier leaf out timings of these tree species in relation to the dates when surveys were performed. While the use of PAM and acoustic indices enabled surveys across multiple sites over longer time periods than would previously have been achievable, our results show that care should be taken when selecting the indices and interpreting acoustic index results. Article data: This folder contains data files associated with the published article and appendices. Excel files contain ACI and BI values that were calculated for the individual audio files recorded in each plot that were used in analyses. Median values for each time period are also included. Audio files provided were used to assess acoustic index bias towards soundscape elements other than bird vocalizations, relationships between acoustic index values and bird species richness (Appendix B), and the effect that distance between source and receiver had on acoustic index values (Appendix C).

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