Abstract
In April 2016, Western EcoSystems Technology, Inc. initiated a bat acoustic survey for the proposed Crocker Wind Farm (Project) in Clark County, South Dakota. The bat acoustic survey conducted at the Project was designed to estimate levels of bat activity throughout the Project during spring, summer, and fall.
Acoustic surveys were conducted using SM3 bat detectors from April 14 to October 27, 2016, at two meteorological tower stations located in agricultural fields. The paired ground and raised met tower stations recorded a combined mean (± standard error) of 1.84 ± 0.22 bat passes per detector-night. Detectors at fixed ground stations recorded 448 bat passes on 265 detectornights for a mean (± standard error) of 1.84 ± 0.23 bat passes per detector-night. Raised stations recorded a similar number (455) of bat passes on 265 detector nights for a mean of 1.83 ± 0.24 per detector-night.
Low-frequency bat species, such as hoary bats and silver-haired bats, composed nearly 67% of bat passes overall. Four bat species and the Myotis group were identified at each of the four full-spectrum SM3 stations using the auto-classifier component of Kaleidoscope 3.1.7. Big brown bats were the least commonly recorded and hoary bats were the most commonly recorded species, present on 31% of detector nights.
Bat activity was also highest in the fall, peaking in early August. Activity during the standardized Fall Migration Period was 2.80 ± 0.42 bat passes per detector-night at ground met tower stations. Most wind energy facilities in the Midwest region have reported fewer than five bat fatalities/megawatt (MW)/year (1.64 – 4.35 bats/MW/year). The results from this study suggest that bat fatality rates at the Project may be fewer than five bats/MW/year, occur mainly in the fall, and mainly be composed of low-frequency species such as hoary bats and silver-haired bats.