WINDPOWER report: Whooping cranes may avoid wind farm

A study of whooping crane and sandhill crane behavior at a wind farm in South Dakota suggests that cranes may avoid wind farms, reducing risk of collision deaths for the iconic endangered whooping crane. However, more data will be needed on whooping crane behavior and on the degree to which avoidance may cause habitat loss as birds steer away from wind farms.

That was the general substance of a presentation yesterday by Laura Nagy, an avian biologist with environmental consulting firm Tetra Tech, at the WINDPOWER 2011 Conference & Exhibition.

The potential for conflict between whooping cranes, a species that currently numbers 279 individuals, and wind power development appears at first glance to be significant. The cranes winter at a wildlife refuge on the Texas Gulf Coast and migrate to central Canada in the summer, with a migratory corridor some 200 miles wide that crosses the windy Plains states.

At the same time, the frequency of collisions of large water birds such as cranes and herons with wind turbines has generally been very low, which in turn raises questions about the effect of avoidance on habitat available to the birds.

The Tetra Tech research was conducted at the Titan I Wind Farm, a project with 10 Clipper Windpower 2.5-MW wind turbines. Since the overall number of whooping cranes is so low that very few if any sightings were expected, the research also looked at sandhill cranes, a much more numerous species with behavior similar to whooping cranes.

As part of the research effort, a monitor drove roads throughout the day on the site during the spring (March 26-May 11, 2010) and fall (September 10-October 31, 2010) migration seasons. In addition to watching for and recording crane movements through and around the site, the monitor’s job was to contact the control center if whooping cranes were seen so that the turbines could be shut down.

In the end, three sightings of small flocks of whooping cranes occurred, two lasting less than five minutes each and one that lasted for three days as the flock was hampered by unfavorable winds.

Much larger numbers of sandhill cranes–a total of 66 flocks numbering more than 4,000 individuals in all–were recorded. The sandhill cranes flew over, around and through the wind project. Ninety-two percent of those flying within the height of the rotor swept area showed avoidance behavior, and even 26 percent of those flying above the rotor swept area changed course.

While a significant number of sandhill cranes passed the site at levels well above the rotors, it is possible that some may have altered their behavior by beginning to fly higher at distances beyond those monitored.

By Tom Gray,