Geographic source of bats killed at wind-energy facilities in the eastern United States

TL;DR

This study identifies the geographic origins of bats killed at wind-energy facilities in the eastern U.S., showing that many are migrants, which highlights the widespread impact of wind energy on bat populations.

Contribution

The study combines stable isotopes, trace elements, and species distribution models to determine the geographic origins of bat fatalities at wind facilities.

Findings

In Maryland, a higher proportion of bats were classified as migrants compared to Ohio.

Results show that wind-energy facilities impact both migratory and resident bat populations.

There is seasonal variation in the proportion of migrants killed and evidence of philopatry to summer roosts.

Abstract

Bats subject to high rates of fatalities at wind-energy facilities are of high conservation concern due to the long-term, cumulative effects they have, but the impact on broader bat populations can be difficult to assess. One reason is the poor understanding of the geographic source of individual fatalities and whether they constitute migrants or more local individuals. Here, we used stable hydrogen isotopes, trace elements and species distribution models to determine the most likely summer geographic origins of three different bat species (Lasiurus borealis, L. cinereus, and Lasionycteris noctivagans) killed at wind-energy facilities in Ohio and Maryland in the eastern United States. In Ohio, 41.6%, 21.3%, 2.2% of all individuals of L. borealis, L. cinereus, and L. noctivagans, respectively, had evidence of movement. In contrast, in Maryland 77.3%, 37.1%, and 27.3% of these same species were classified as migrants. Our results suggest bats killed at a given wind facility are likely derived from migratory as well as resident populations. Finally, there is variation in the proportion of migrants killed between seasons for some species and evidence of philopatry to summer roosts. Overall, these results indicate that the impact of wind-energy facilities on bat populations occurs across a large geographic extent, with the proportion of migrants impacted likely to vary across species and sites. Similar studies should be conducted across a broader geographic scale to understand the impacts on bat populations from wind-energy facilities.

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