Wind power development is an emerging issue in northeastern Minnesota. A recent Coastal Zone Management Program (CZMP) study showed strong potential for wind energy along the North Shore, even though wind speed maps indicate that northeastern Minnesota has less wind potential than other parts of the state. There are seven bat species in Minnesota, and all of them could be affected by wind power development. Baseline data on bat distribution and habitat use is essential for bat conservation. Little information exists on bats in the southern boreal forests of the Midwest. We measured summer bat habitat use and foraging activity at aquatic, linear corridor, and interior forest sites with bat detectors in deciduous, mixed-wood, and coniferous forests in northeastern Minnesota. We used three common acoustic bat activity indices to quantify acoustic bat data and examined the indices to determine how differences among activity indices influence statistical inferences of bat activity. We measured the effects of relative insect abundance and degree of vegetation density on bat activity. Bat detectors recorded 7,666 identifiable bat calls during 1,440 detector hours in 2009 and 8,554 bat calls during 930 detector hours in 2010. Bat activity was dominated by Myotis species (Myotis lucifugus and M. septentrionalis) and Lasionycteris noctivagans. Activity was concentrated at aquatic and linear corridor microsites, regardless of forest cover type. However, bats foraged at similar rates in each microsite type. Bat activity and foraging activity occurred earlier at night at interior forest sites relative to aquatic and linear corridor sites, suggesting that interior forest is used by bats to forage as they leave day roosts. The three acoustic activity indices we used resulted in similar conclusions of habitat use by bats, despite different biases of each. Bats would generally be flying in low wind conditions, especially when foraging. If wind turbines were deployed along the North Shore, we recommend monitoring bat activity to document potential effects at the site(s). However, because all bat species were present along the entire north shore of Lake Superior inland throughout the Coastal Zone area, wind turbines are unlikely to have a population level effect on bats unless many are installed.
Minnesota’s Lake Superior Coastal Program; Project No. 306-14-11; Contract No. b31556
Abel, Rebecca; Moen, Ronald.
North Shore bat activity and habitat use.
University of Minnesota Duluth.
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