ABSTRACT
Wind turbines have been hypothesized to affect bat populations; however, no comprehensive analysis of bat mortality from the operation of wind turbines in Canada has been conducted. We used data from carcass searches for 64 wind farms, incorporating correction factors for scavenger removal, searcher efficiency, and carcasses that fell beyond the area searched to estimate bat collision mortality associated with wind turbines in Canada. On average, 15.5 ± 3.8 (95% CI) bats were killed per turbine per year at these sites (range = 0−103 bats/turbine/yr at individual wind farms). Based on 4,019 installed turbines (the no. installed in Canada by Dec 2013), an estimated 47,400 bats (95% CI = 32,100−62,700) are killed by wind turbines each year in Canada. Installed wind capacity is growing rapidly in Canada, and is predicted to increase approximately 3.5-fold over the next 15 years, which could lead to direct mortality of approximately 166,000 bats/year. Long-distance migratory bat species (e.g., hoary bat [Lasiurus cinereus], silver-haired bat [Lasionycteris noctivagans], eastern red bat [Lasiurus borealis]) accounted for 73% of all mortalities. These species are subject to additional mortality risks when they migrate into the United States. The little brown myotis (Myotis lucifugus), which was listed as Endangered in 2014 under the Species At Risk Act (SARA), accounted for 13% of all mortalities from wind turbines, with most of the mortality (87%) occurring in Ontario. Population-level impacts may become an issue for some bat species as numbers of turbines increase. © 2016 The Wildlife Society.
Studying migratory behavior of bats is challenging. Thus, most information regarding their migratory behavior is anecdotal. Recently, however, fatalities of migratory bats at some wind energy facilities across North America have provided the opportunity and impetus to study bat migration at fine spatial and temporal scales. Using acoustic monitoring and carcass searches, we examined temporal and spatial variation in activity levels and fatality rates of bats at a wind energy facility in southern Alberta, Canada. Our goals were to better understand the influence of weather variables and turbine location on the activity and fatality of hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans), and to use that understanding to predict variation in fatality rates at wind energy facilities and recommend measures to reduce fatalities. Overall activity of migratory bats and of silver-haired bats increased in low wind speeds and warm ambient temperatures, and was reduced when the wind was from the North or Northeast, whereas hoary bat activity increased with falling barometric pressure. Fatalities of migratory bats in general increased with increased activity of migratory bats, increased moon illumination, and falling barometric pressure and were influenced by the interaction between barometric pressure change and activity. Fatalities of silver-haired bats increased with increased activity, moon illumination, and winds from the south-east. Hoary bat fatalities increased with falling barometric pressure. Our results indicate that both the activity and fatality of migratory bats are affected by weather variables, but that species differ in their responses to environmental conditions. Spatially, fatalities were not influenced by the position of turbines within a turbine row, but were influenced by the location of turbines within the facility. Our findings have implications for our understanding of bat migration and efforts to reduce fatalities at wind energy facilities. To maximize the reduction of bat fatalities, operators of wind energy facilities could incorporate migratory bats' response to environmental variables, such as barometric pressure and fraction of moon illuminated, into their existing mitigation strategies. © 2011 The Wildlife Society.
Abstract
Large numbers of migratory bats are killed every autumn at wind energy facilities in North America. While this may be troubling from a population perspective, these fatalities provide an opportunity to learn more about bat migration and the origins and summer distributions of migratory bats by using endogenous markers. Such markers include stable isotope values, which have been used to answer questions about ecological systems, such as trophic levels and food webs, and the origins and migratory routes of animals. To estimate the origins of migratory bats, we determined nitrogen (δ15N), carbon (δ13C), and hydrogen (δ2H) stable isotope values of fur (δ15Nf, δ13Cf, δ2Hf, respectively) from hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) killed at a wind energy facility in southern Alberta, Canada. We determined that mean isotope values varied among species, year, sex, and age class. δ13Cf and δ2Hf values indicated that silver-haired bats likely originated in the boreal forest, farther north and/or at higher elevations than the aspen parkland-like habitat suggested by the isotope values of hoary bats. IsoMAP analysis indicated that bat fatalities may have originated from a large catchment area potentially hundreds of kilometers away. Our data provide further evidence for a migration route along the eastern slopes of the Rocky Mountains that is used by bats from across Alberta and beyond, and suggest that fatalities at a single wind energy site have the potential to have far-reaching ecological and population consequences.
COMMENTS