An evaluation of bird and bat mortality at wind turbines in the Northeastern United States

Abstract

Wind energy offers substantial environmental benefits, but wind facilities can negatively impact wildlife, including birds and bats. Researchers and managers have made major efforts to chronicle bird and bat mortality associated with wind facilities, but few studies have examined the patterns and underlying mechanisms of spatial patterns of fatalities at wind facilities. Understanding the horizontal fall distance between a carcass and the nearest turbine pole is important in designing effective search protocols and estimating total mortality. We explored patterns in taxonomic composition and fall distance of bird and bat carcasses at wind facilities in the Northeastern United States using publicly available data and data submitted to the US Fish and Wildlife Service under scientific collecting and special purpose utility permits for collection and study of migratory birds. Forty-four wind facilities reported 2,039 bird fatalities spanning 128 species and 22 facilities reported 418 bat fatalities spanning five species. Relative to long-distance migratory birds, short-distance migrants were found farther from turbines. Body mass of birds and bats positively influenced fall distance. Turbine size positively influenced fall distance of birds and bats when analyzed collectively and of birds when analyzed separately from bats. This suggests that as turbines increase in size, a greater search radius will be necessary to detect carcasses. Bird and bat fall distance distributions were notably multimodal, but only birds exhibited a high peak near turbine bases, a novel finding we attribute to collisions with turbine poles in addition to blades. This phenomenon varied across bird species, with potential implications for the accuracy of mortality estimates. Although pole collisions for birds is intuitive, this phenomenon has not been formally recognized. This finding may warrant an updated view of turbines as a collision threat to birds because they are a tall structure, and not strictly as a function of their motion.

An Updated Review of Hypotheses Regarding Bat Attraction to Wind Turbines

“…Some evidence of foraging activity along migratory routes has been observed through tracking the movement of radio-tagged individuals [55][56][57], stable isotope analysis [58], and direct observation [59]. This may explain greater rates of mortality due to wind turbines for migratory compared to non-migratory bat species [5,8,60,61].…”

“…One consequence of wind energy development is bat mortality caused by wind turbine blade strikes, and increasing development of wind energy represents a relatively new stressor to numerous bat species, sparking concern among conservationists and private industries [4]. In North America, migratory tree-roosting species, including the hoary bat (Lasiurus cinereus), eastern red bat (Lasiurus borealis), and silver-haired bat (Lasionycteris noctivagans), constitute most of the bat carcasses reported in the U.S. and Canada from wind turbine strikes, and therefore are thought to be currently the most vulnerable to wind turbinerelated mortality in these countries [5][6][7][8][9]. Additionally, wind turbine strikes are known to cause the mortality of protected species, including the Hawaiian hoary bat (Lasiurus semotus) [10,11].…”

Monitoring and Modeling Tree Bat (Genera: Lasiurus, Lasionycteris) Occurrence Using Acoustics on Structures off the Mid-Atlantic Coast—Implications for Offshore Wind Development

“…Collisions with wind turbines are an expanding conservation concern for bats [ 1 , 2 , 3 ]. In North America, non-hibernating, migratory “tree bats” (Genera: Lasiurus and Lasionycteris ) are particularly susceptible to collisions and are often the majority bat group in post-construction carcass surveys at wind energy facilities [ 4 , 5 , 6 , 7 , 8 ]. The tree bat mortality rate at wind turbines appears to be highly correlated with the seasonal movements of these species [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ] whereby collisions are generally elevated in spring and maximized in fall migration periods [ 5 , 7 , 16 ].…”

Bat Mortality in Wind Farms of Southern Europe: Temporal Patterns and Implications in the Current Context of Climate Change

“…Kruszynski et al 2022). However, information on the impact of this human infrastructure on bats is still scarce and fragmented, as very few facilities report bat mortality data (Gaultier et al 2020;Choi et al 2020). In this study, we analysed an extensive database containing more than ten years of information on bat mortality at different wind farms, all of them located in the extreme south-west of Europe.…”