Do wind turbines kill birds?

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A bird of prey soars over wind turbines in New Zealand.
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A bird of prey soars over wind turbines in New Zealand. See more green science pictures.

With U.S. dependency on foreign oil getting uncomfortably close to crisis levels, any viable alternative energy source is looking pretty good. With environmental damage from coal and gas-derived power already at crisis levels, even alternatives that are decades off are looking pretty great. Wind power, a viable energy source that costs far less than nuclear and coal power and contributes almost no pollutants to the environment, seems to many of us to be almost ideal.

But there are some people who disagree and are fighting the installation of new wind turbines in the United States. They cite bird mortality as an unacceptable side effect of wind-generated power. Through lawsuits and protests against pending legislation, they hope to save huge numbers of birds from death at the blades of massive wind turbines.

To most experts, though, there's a problem with the bird-mortality argument: The vast majority of research shows that wind turbines kill relatively few birds, at least compared with other man-made structures. The statistics are shocking if you consider just how many people are crying out against wind power for the birds' sake:

Man-made structure/technology

Associated bird deaths per year (U.S.)

Feral and domestic cats

Hundreds of millions [source: AWEA]

Power lines

130 million -- 174 million [source: AWEA]

Windows (residential and commercial)

100 million -- 1 billion [source: TreeHugger]

Pesticides

70 million [source: AWEA]

Automobiles

60 million -- 80 million [source: AWEA]

Lighted communication towers

40 million -- 50 million [source: AWEA]

Wind turbines

10,000 -- 40,000 [source: ABC]


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Collisions with wind turbines account for about one-tenth of a percent of all "unnatural" bird deaths in the United States each year. And of all bird deaths, 30 percent are due to natural causes, like baby birds falling from nests [source: AWEA]. So why the widespread misconception that labels wind turbines "bird-o-matics"? I­t all starts with California, raptors and the thousands of old turbines that make up the Altamont Pass wind farm.

­In this article, we'll find out where the statistics went wrong, how thousands of birds do end up flying into wind turbines each year and what's being done to reduce the number of bird-turbine collisions.

 

The Problem with Wind Turbines

The Altamont Pass in California.
Phil Schermeister/National Geographic/Getty Images
The Altamont Pass in California is known for its outdated turbines and high avian mortality rate.

It's easy to see why wind turbines are at least potentially hazardous for birds: Massive blades with tips spinning at up to 179 mph (80 meters per second), hundreds of feet (at least 30 meters) in the air, are an obvious problem for anything flying near them [source: MIT]. The fact is, birds do fly into the path of the blades and die a grisly death. Most of the affected birds are songbirds, and about 10 percent are birds of prey like raptors [source: ABC]. It's the raptors that started all the protests, when hundreds of carcasses were found strewn across Northern California's Altamont Pass wind farm.

Bird conservationists took great interest, and the misconception that wind turbines pose a major threat to bird populations grew from there. By applying the mortality rates at Altamont Pass to every wind farm in the United States, the bird-mortality figures became extremely inflated. In fact, Altamont Pass is a unique case of a wind farm that is truly a significant hazard to birds.

Altamont Pass is different for two main reasons: turbine location and turbine design.

There are more than 4,000 wind turbines at the Altamont Pass energy farm in California. It's one of the first wind farms in the United States, and its 20-year-old turbines are accordingly out-of-date. Their design has long since been abandoned: Latticework blades with small surface area are far from efficient for energy generation, and far from safe for birds. The lattice structure actually attracts large birds, because the frame makes for an excellent perch. Large birds like raptors are drawn to the blades, and collision rates are high as a result.

The other design issue is the blades' low surface area, because less surface area means the blades have to spin faster to turn the electricity-generating turbines. The faster the blades spin, the more dangerous they are to birds flying near them. It's unlikely that a bird that finds itself in the vicinity of the blades could ever make it through when they're spinning so fast.

As if this weren't enough to make old wind farms a bird nightmare, the Altamont Pass power plant was built smack dab in the middle of a major migratory route for large birds. The area also houses the world's largest single population of golden eagles [source: USA Today]. With thousands of dated wind turbines sprawling across a super-high-population bird area, it's inevitable that birds and turbines will meet. A current estimate puts the number of birds killed by turbines at Altamont Pass to be about 4,700 each year, several hundred of which are raptors [source: USA Today].

The Altamont Pass wind farm kills far more birds than any other farm in the United States. The total at that single wind farm with 4,000 turbines is 4,700 fatalities; the total for all wind farms in the United States, with more than 25,000 turbines in operation at any given time, is 10,000 to 40,000 per year [source: Reuters].

­Even though up to 1 billion birds die each year by flying into windows, no one is brushing off the tens of thousands of turbine-related deaths every year. So what are we doing to lower that number? On the next page, we'll see what changes are being implemented to save the birds.

Location, Location and Surface Area

Tug Hill.
Frank Whitney/Photographer's Choice/Getty Images
Newer turbines, like those on Tug Hill in New York, have a larger surface area and cause fewer bird deaths.

In the past couple of decades, turbine designs have changed dramatically. Turbine blades are now solid, meaning no lattice structure to attract birds looking to perch. Also, the blades' surface area is much larger, so they don't have to spin as fast to generate power. Slower-moving blades mean fewer bird collisions.

Perhaps the biggest change in wind-farm safety, though, has to do with location. Now, all new turbine proposals are reviewed for ideal, bird-friendly placement. Wind farms cannot be built in migratory pathways, in areas with high bird populations, or in areas with special features that could possibly attract high bird populations in the future. Also, the growing trend toward offshore turbine construction bodes well for birds, since offshore wind farms have fewer bird collisions than land-based farms.

Turbines and Bats
Bats have many of the same habits and habitats as birds. They just come out at night instead of day. It logically follows that bats would have run-ins with wind turbines, too; and they do, more often than birds at some locations. Still, most experts see the numbers as negligible compared to bat deaths by other forms of human intervention. According to the American Wind Energy Association, it's not just pollution and habitat destruction. People accidentally waking bats from their daytime sleep kills far more bats than wind turbines ever could. Apparently, sleep disruption messes up bats' metabolism, causing many of the little guys to starve in winter [source: AWEA].

Possibly the greatest indicator that wind turbines are not, in fact, bird-o-matics, is the growing number of endorsements by bird conservation groups. The American Bird Conservancy supports wind power with the caveat that bird-friendly placement and design be primary factors in construction [source: ABC]. The Wisconsin Bird Initiative states that wind turbines have a "low impact" on avian mortality compared to window glass and communication towers [source: WBCI]. And in 2006, the Audubon Society gave its figurative seal of approval to the American Wind Energy Association. The president of the national organization is quoted by Renewable Energy World as stating, "When you look at a wind turbine, you can find the bird carcasses and count them. With a coal-fired power plant, you can't count the carcasses, but it's going to kill a lot more birds" [source: REW].

Of course, zero turbine-related bird deaths would be the best-case scenario, but as far as energy production goes, that seems to be an unrealistic goal. The best we can hope for is smarter placement of wind turbines and more bird-friendly design in order to further reduce the number of bird deaths resulting from one of the best alternative energy sources available right now. Altamont Pass, for its part, is in the process of slowly replacing its turbines with newer models.

For more information on wind energy and birds, fly to the links on the next page.

Lots More Information

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Sources

  • Bats and Wind Turbines. American Wind Energy Association.
    http:­//www.awea.org/faq/sagrillo/ms_bats_0302.html
  • Common Eco-Myth: Wind Turbines Kill Birds. TreeHugger. April 6, 2006.
    http://www.treehugger.com/files/2006/04/common_misconce.php
  • For the Birds: Audubon Society Stands Up in Support of Wind Energy. Renewable Energy World. December 14, 2006.
    http://www.renewableenergyworld.com/rea/news/story?id=46840
  • Massive Offshore Wind Turbines Safe for Birds. Technology Review. MIT. February 12, 2007. ­ ­
    http://www.technologyreview.com/Energy/18167/
  • Mortality Threats to Birds: Wind Turbines. American Bird Conservancy.
    http://www.abcbirds.org/conservationissues/threats/energyproduction/wind.html
  • Putting Wind Power's Effect on Birds in Perspective. American Wind Energy Association.
    http://www.awea.org/faq/sagrillo/swbirds.html
  • Quietly, wind farms spread footprint in U.S. Reuters. May 19, 2008.
    http://www.reuters.com/article/latestCrisis/idUSN18351503
  • Wind Power and Birds. Wisconsin Bird Conservation Initiative.
    http://www.wisconsinbirds.org/WindPowerandBirds.htm
  • Wind turbines taking toll on birds of prey. USAToday. January 4, 2005.
    http://www.usatoday.com/news/nation/2005-01-04-windmills-usat_x.htm