Wind Turbines Hard on Bats

Tall wind turbines that generate energy are killing bats more than birds. As many as 43 bats crash fatally into the rotating blades of a turbine each a year.

This amounts to over 1875 bat deaths annually at an installation of 44 turbines in West Virginia.

In comparison, the highest bird death rate documented for a tower on the continent is nine birds a year in Tennessee. These findings are from data collected at 33 wind energy sites in 17 North American states and provinces.

Shorter towers kill relatively few birds and bats, typically one or two a year. Yet once towers reach over 65 metres (213 feet) in height, far more bats, although not birds, get hit. The difference can be explained by the tendency of bats to fly lower than birds. Wind turbines higher than 65 metres extend into the airspace that bats use.

Bat accidents always occur at night and usually during their fall migration. For some unknown reason, the bats' echolocation seems to fail with moving blades, especially those rotating in gentle winds. The size of the turbine blades, though, has no bearing on how lethal the structure is to airborne animals.

Most of the bats killed at wind turbines are from three species: hoary bats, eastern red bats and silver-haired bats. With the recent trend to building taller wind turbines, well over 65 metres in height, these three bat species could be hit hard.


Robert M.R. Barclay, E.F. Baerwald and J.C. Gruver. 2007. Variation in bat and bird fatalities at wind energy facilities: assessing the effects of rotor size and tower height. Canadian Journal of Zoology. 85(3): 381-387.

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