Grassland bird community and acoustic complexity appear unaffected by proximity to a wind energy facility in the Nebraska Sandhills

Abstract

The placement of wind energy facilities on the landscape is a potential source of direct mortality for wildlife, but indirect effects of wind facilities on natural communities are less well known. An anthropogenically altered acoustic environment may render habitat unsuitable for species that use vocalizations to communicate. We listened to sound recordings to identify the species assemblage of common breeding birds in an unfragmented grassland in the Nebraska Sandhills (USA) in the vicinity of a wind energy facility. From the recordings, we calculated the Acoustic Complexity Index (ACI), which we used to assess differences in the avian community between a reference area (>760 m from any turbines) and a treatment area (<760 m from turbines). We did not observe differences at the assemblage level using univariate metrics of diversity: mean species richness (3.48 vs. 3.25 species per recording event) and Whittaker βw index (6.03 vs. 5.85 species turnover of habitat type) or the ACI (0.17 vs. 0.15). ACI increased with the progression of the breeding season and was correlated with species richness, indicating that ACI provides a useful estimate of acoustic activity of grassland songbirds. The limited habitat perforation caused by wind energy facilities and roads (1% in the area of the wind energy facility) and the low-frequency noise emitted by operational wind turbines did not appear to affect the presence or singing behavior of breeding passerine birds in this landscape.