Bat fatalities at wind-energy facilities have been documented since the early 1970s. Previous studies have documented high fatality rates along forested ridges in the eastern United States (e.g., Mountaineer, WV, Kerns et al. 2005; Buffalo Mountain, TN, Fiedler 2004, Fiedler et al. 2007). However, recent data suggests high fatality events occur across a variety of landscapes across North America, including agricultural, grassland prairies, and deciduous or coniferous forests. Most bat fatalities documented at wind farms involve migratory tree-roosting species [i.e., hoary (Lasiurus cinereus), Eastern red (Lasiurus borealis), big brown (Eptesicus fuscus), and silver-haired (Lasionycteris noctivagans)] bats during seasonal periods of migration in late summer and fall. Several hypotheses explaining possible bat/turbine interactions exist (i.e., roost, landscape, acoustic or visual attraction), however, none have been tested. The lack of data on population estimates, migratory pathways, and flight behaviors around wind turbines of North American bats highlights the need for additional information to resolve these different hypotheses.
The primary goal of the study was to collect acoustic information on activity levels of bats during nocturnal hours, particularly during spring and fall migration. Specifically, our objectives were to: (1) collect baseline information on levels of bat activity (i.e., # bat passes/h, night, or tower) for migratory tree-roosting bats (e.g., hoary, Eastern red, and big brown/silver-haired bats) and other bat species (mainly Myotis spp.); and (2) examine spatial (height and location) and temporal (e.g., nightly and seasonal) variations in bat activity.