Wind Turbines Spin a Web of Worries for Hawk Watchers

By Will Weber, Hawk Migration Association of North America, Hawk Migration Association of NA

Not every one sees wind turbines as clean, ecologically safe, energy machines. Some hawk watchers across North America fear wind turbines may be the biggest man-made threat to raptors, other birds and bats since DDT caused massive population declines in the 1960’s. Unfortunately, many of the windiest locations preferred by wind energy developers are already being used by migratory birds and bats that never evolved navigation mechanisms capable of dealing with huge swirling blades.

Each Spring and Fall thousands of hawk watchers seek windy lookouts on ridge tops and shorelines to monitor the breeze-driven migration of about 30 species of hawks, eagles and other large birds. Rather than unobstructed views of gliding raptors, many of these observers are looking at new wind turbines or formerly wooded sites being cleared for turbine development. The vision is frightening.

While corporate, municipal and utility interests favoring wind turbine development tend to minimize potential damage to birds, no convincing scientific studies support arguments that wind turbines in migration corridors are safe. Quite the contrary, mounting evidence suggests birds and bats are at risk of fatal collisions with turbine blades. In recent testimony before the U.S. Congress, Dr. Michael Fry of the American Bird Conservancy concluded that by the year 2030 as many as 1.8 million birds per year could be killed by wind turbines.

Hawk watchers are not opposed to wind turbines sited in locations carefully selected to minimize the chance of collisions. The recurrent experience of many groups, however, has found local municipalities and turbine proponents unwilling to compel adequate siting studies or even to accept the possibility that wind turbines are capable of posing dangers to wildlife. This unwillingness persists even in the absence of any research proving turbines safe for migrating birds and bats.

Champions of migratory birds are worried about the scarcity of adequate pre-construction studies. At any location, the presence of wind-loving migrants varies by species, time of day and year, weather, and vegetation conditions, so adequate study of collision risk requires observation through whole seasons and several years, not the limited hours of non-expert observation typically cited in most feasibility studies. Hawk watchers, who do observe all day, every day, season after season and year after year, are very concerned about the lack of scientific rigor in typical preconstruction studies, a lack of rigor allowing conclusions that fail to paint an accurate picture of risk.

Deficient pre-construction studies at the wrong time of year or day or in the wrong weather may not detect migrating birds in the area at all. Experienced migration observers will tell you that more than 50 percent of the total seasonal passage of some species may occur in just a few days or even hours and it would be at these times of high density migration when deaths would most likely occur. These few hours of migration are an easy window to miss for poorly designed or executed preconstruction studies.

Young birds may be particularly susceptible to destruction when they encounter a wind turbine for the first time. Hawk watchers note hatchling year birds are less agile flyers but represent a large fraction of the migrant population. Last year a wind turbine project off the coast of Norway was particularly fatal to immature sea eagles. The poorly sited project all but eradicated the resident population of white-tailed eagles, killing nine eagles in 10 months, including all the region’s first-year birds, and apparently causing the decline of breeding pairs in the vicinity from 19 to one pair.

Raptor biologists caution that even if birds learn to divert around wind turbines, doing so may require extra energy or expose them to other risks. For example, many raptors do not like to fly over water where they lose thermal lift or are exposed to predation from other raptors. Some species critically depend on strong updrafts along shores or ridges where winds often are best for turbine operation

Wind turbines are most efficient when the winds are strong. But the windiest days present the greatest threat to migrating raptors. On windy days blades spin faster, slicing the same area more times per minute. Birds that soar and migrate at great heights in light winds will be forced to fly at much lower levels and will have less control of their flight in heavy winds or in the erratic bluster of an approaching storm front. For many species, these are preferred migration conditions, presuming the absence of 400-foot tall sky slicers in their path.

Hawk watchers find their own concerns echoed in the experience and alarm of bat observers. Bats’ sonar may signal safe passage ahead just as a turbine blade suddenly cuts them in half. Songbirds, migrating unseen at night, often follow the same migration corridors as raptors in the day. Little is known about their susceptibility to wind turbine collisions, although recent post-construction studies at a 120-turbine project on the Tug Hill plateau in New York State found much higher songbird mortality than anticipated, more than 2,000 birds in one year. The same project also killed many more bats than expected, with nearly 6,000 bats killed over the same year.

Wind turbines have become symbols of the quest to provide abundant power without pollution or carbon emissions. For many of us, however, they are a disturbing repetition of mankind’s tendency to naively and fanatically embrace new and wonderful but poorly understood technologies. Without understanding the potential downside, we want to jump to the conclusion that something so powerfully good must be able to solve our problems and make life better. This was the naive hope for DDT, until we realized the dark and slippery downside of dramatically altering the chemistry of our biosphere.

Wind turbines might make economic sense in some situations, but we must avoid placing them where they could cause ecological catastrophes.

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  • Posted on Aug. 28, 2007. Listed in:

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