Recent data from Appalachian ridge tops in the eastern US, the Tug Hill Plateau region in New York, prairie locations in both the US and Canada, have indicated that substantial bat kills are also possible at wind power projects. These unexpected collisions have prompted researchers to develop standard methods for assessing bat use of proposed wind power projects. Most of the bat fatalities documented at wind farms have been associated with 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 dispersal and migration in late summer and fall, and several hypotheses have been posited, but not tested, to explain bat/turbine interactions. Limited evidence suggests that bats may be killed when flying straight into objects (and not reacting) and their movement rates (or foraging activity at or below turbines), therefore, may be correlated with their fatality rates. There are many possible hypotheses as to why bats may collide with wind turbines including the idea that bats are using large, modern, wind turbines as rendezvous sites during the fall mating season. The lack of information on migratory pathways, measures of abundance, flight altitudes, and flight behaviors for migratory tree-roosting bats in North America highlights the need to obtain this critical information.
The primary goals of this study were to collect visual and acoustic information on both the flight characteristics and activity levels of migratory and resident birds (especially passerines) and bats during nocturnal hours of fall migration. Specifically, the objectives of this study were to: (1) collect baseline information on flight characteristics (i.e., flight directions, observation rates, flight altitudes) of birds and bats flying at night with visual methods; (2) estimate the relative proportions of birds and bats at low altitudes (≤ ~ 150 m agl) with visual methods; (3) 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 species (mainly Myotis spp.) of bats.