BEND, Ore. (AP) — A university study says a Pacific Northwest bat that that migrates south for the winter faces a serious threat from wind turbines.

The Bend Bulletin reports a study by Oregon State University-Cascades concludes that the hoary bat faces an uncertain future because its numbers have declined by 2% per year.

A study author, Tom Rodhouse, says bats can be killed by collisions with propellers and by barotrauma, which occurs when bats fly through low pressure zones created by spinning blades of a wind turbine.

The sudden change in pressure causes bats' lungs to expand faster than the bats can exhale, resulting in burst vessels that fill their lungs with blood.

Rodhouse says hoary bats often fly into danger zones because their sophisticated sonar capabilities can't detect pressure drops.