TADS was mounted on a Nysted wind-farm turbine that was situated in the most common flight path, and during more than 2,400 hours of monitoring that concluded last fall, it spotted only fifteen birds and bats and one moth flying near the turbine, and it recorded one collision involving a small bird or bat. Furness says that this provides confidence in estimations by Danish researchers that the Nysted wind farm would kill few common eiders.
The Danes’ clean bill of health is boosting prospects for the Cape Wind project because its ecosystems are similar; in particular, many of the bird species they observed also frequent Nantucket Sound. In contrast, most estimates of Cape Wind’s impact on Nantucket Sound’s rich bird life have been extrapolated from studies of onshore wind farms, leaving plenty of room for disagreement. In a draft environmental assessment issued in 2004, the U.S. Army Corps of Engineers estimated that Cape Wind would kill no more than 364 birds per year, whereas Mass Audubon argued that the data could just as easily predict mortality as high as 6,600 birds per year.
Allison says that TADS and the Danish study as a whole have now narrowed the range of probable impacts. “We certainly haven’t seen any mass mortality event,” Allison notes. A second environmental assessment for Cape Wind, expected imminently from the U.S. Department of the Interior, will include the Danish results.
Nevertheless, Allison insists that Cape Wind must perform its own studies to confirm the project’s safety. Furness agrees: “The problem of bird collisions is rather site specific. The industry would like to say, ‘Oh well, the Danes have done it, so we don’t have to worry about it.’ I don’t think that’s a reasonable approach.”