Abstract
On a warm, late-April night, Volker Kelm drives his battered station wagon across a bleak expanse of scrubby fields a few kilometers from the German border with Poland. The site is a brown coal strip mine owned by the German energy giant Vattenfall; the only other vehicles on the access roads are massive earthmovers. The Berlin-based environmental consultant parks on a dirt access road and pulls out what looks a bit like an old-fashioned tape recorder but is actually a monitor capable of picking up ultrasonic calls from bats ranging up to 120 kilohertz.
Tuning the detector to the 32-kilohertz range favored by Nyctalus noctula, one of Europe's most common bat species, Kelm starts scanning the sky. At 20:59, just as the day's last light dwindles away, the bat detector begins to chirp. Kelm watches as a trio of Nyctalus bats—known as the common noctule all across Europe—makes their way across the field in the direction of a long line of blinking red lights on the horizon: dozens of wind energy turbines, a night's flight away.