Wind power is considered a viable alternative to fossil fuels for electricity generation. But one of the main objections to the installation of the turbines, which can be hundreds of feet high, is the effect they may have on birds and other wildlife.
In 1998, planning began for the Horns Rev wind farm in the North Sea, off the coast of Denmark. Construction of its 80 turbines was completed in 2002. Environmentalists and others were worried about the large number of birds that migrated through the area. But an in-depth study using visual and radar observation, conducted by Denmark's National Environmental Research Institute over a two-year period, showed that the turbines posed little risk to migrating birds.
"The low number of seabirds and waterfowl recorded inside the wind farm by migrating birds recorded by radar, indicate that most bird species generally exhibit an avoidance reaction to wind turbines, which reduces the probability of collision," the study said. According to the study, most birds altered their flight pattern around 100-200 meters before the turbines, and then passed above the farm at a safe distance.
The same research group also conducted a study at the Nysted wind farm in southern Denmark, which yielded similar results.
Drawing upon the European research, the first offshore wind farm slated for the United States -- a 130-turbine Cape Wind in Massachusetts -- hired Avian Radar, a division of Florida-based Geo Marine, to conduct bird-tracking research.
To track the birds, two radar antennas were placed on Cape Pogue near Horseshoe Shoal on Nantucket Sound, the proposed site of the farm. The antennas are operating nearly 24 hours a day. Avian Radar also is using airplanes and boats for human observations. Cape Wind's study, which has garnered results similar to those in Denmark so far, is set to conclude in late 2005.
Not only were the studies from Denmark a source of baseline information for Cape Wind, but the birds that frequented the Denmark farm, such as winter sea ducks, also travel through Nantucket Sound. At least one environmental group has found the studies reassuring.
"We've read the Denmark studies and viewed those sites, and we put a lot of credibility in the data that's coming out of Europe," said Jack Clarke, director of public policy and government relations at the Massachusetts Audubon Society.
Much of the concern over whether wind farms harm birds was caused by the 7,000-turbine Altamont Pass wind farm in central California, which became notorious among conservationists in the 1990s for killing thousands of birds, most notably raptors, golden eagles and red-tailed hawks.
But changes to onshore and offshore wind power technology have occurred since that farm was built in the early 1980s when blades were shorter and lower to the ground, and therefore had to move faster to produce the same amount of energy. Birds can more easily spot slower, larger modern blades.
In the California farm, the turbines also were only roughly 25 feet apart, whereas in the Cape Wind project, the turbines would stand nearly a half mile apart. The pylons of the Altamont turbines were made of a latticework structure that eagles used for nesting, but Cape Wind's pylons and other newer wind farms utilize solid tubes.
The Massachusetts Audubon Society was initially worried about Cape Wind because one species in the area, the Roseate Tern, is on the federal endangered species list, and several others that may soon be on the list frequent the area, the group said.
The federal regulating agency for Cape Wind's offshore site, the Army Corps of Engineers, drafted an Environmental Impact Statement in February 2005, which found no serious risk to the Roseate Tern or other bird species. Upon examining the EIS, Mass Audubon decided to launch its own study and similarly has found no real problems related to birds.
"If it looked like these birds were going to be further jeopardized in the northeast as a result of this project then we would have some very, very serious concerns and strong doubts about whether it's a viable project," Clarke said. "But we don't see that. Our three years of data shows that the majority of Roseate Terns, as they migrate around that area, avoid Horeseshoe Shoal."
Meanwhile, Cape Wind must undergo another round of federal permitting under the Interior Department's Minerals Management Service, which received authority for regulating alternative energy use of the outer continental shelf -- an area of submerged federal land three miles from shore -- under the Energy Policy Act of 2005. The new layer of approval has delayed Cape Wind's planned completion from 2006 to 2009.
Other environmentalists that support alternative sources of energy and the Cape Wind project specifically, were still cognizant of the potential threat to wildlife.
"Were we to have a shred of evidence that this was going to somehow damage the marine ecosystem of Nantucket Sound, we would be the first environmental organization to say 'not here,'" said Chris Miller, a climate and energy campaigner for Greenpeace International.
According to Miller, Greenpeace has found that on average, the average wind turbine kills between one and three birds a year, which makes turbines far less dangerous than cars, buildings and cats.
"We think this is a perfect place for America's first offshore wind farm," Miller said.
Miller and others closely involved in the project make clear that studying a wind farm's location is vital to ensuring a safe place for animals that live in or travel through the area.
Wind power often poses a dilemma for conservationists, who must carefully weigh their options. There may be consequences for surrounding wildlife when imposing man-made structures are built in a pristine area, but there might also be different and potentially far greater impacts on climate change if the turbines are never built in the first place and fossil fuels are used instead.
Most experts involved with the Cape Wind project assert that such long-term benefits far outweigh smaller and more immediate problems.
"On any of these 'first of its kind' projects that we don't have experience with here in the U.S., I appreciate the fact that some groups are taking a close look at bird casualties," Miller said.
Concerns over bird safety may never fully be addressed until the Cape Wind project is operational, according to Cape Wind communications director Mark Rodgers. "I think what will end those concerns is the successful operation of this wind farm and its actual track record. Then, we'll really know."