Birds and Bats
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Birds and Bats
Do wind farms present a collision risk to birds?
What are the other risks?
What do we know about the impact of wind farms on birds and bats?
What is the experience in New Zealand?
Do wind farms present a collision risk to birds?
Wind turbines, like virtually all man-made structures, present a collision risk to birds and bats although in New Zealand birds are much more prevalent than bats. The risks are far lower than many may imagine - especially when compared to the risk of collision with other structures such as communications towers, tall buildings, cars and transmission towers. The impact of wind turbines on birds and bats is insignificant when compared to the impact of domestic cats and the loss of habitat through development, over-fishing or even more dramatically, the chronic impact of ecological damage due to climate change and rises in sea level induced by the ongoing and extensive release of greenhouse gases. In New Zealand collision rates are at the very most about 1-2 birds per turbine per year although the recorded rates of bird impacts are well below even this level.
What are the other risks?
Wind farm construction and/or operation may impact on the way birds move about in a particular area. This might include direct impacts on light, breeding and feeding behaviour as well as indirect impacts due to disturbance associated with construction activity and noise.
What do we know about the impact of wind farms on birds and bats?
Today bird mortality from wind turbines is probably one of the best-researched areas of risk to avian species. There were undoubtedly some bad experiences in the early days of the wind industry (the 1970s and 1980s) in the United States, particularly around the Altamont Pass region, where wind farms were constructed with little or no understanding of potential bird impacts. Nonetheless today environmental scientists agree that properly sited modern wind farms present minimal danger to bird and bat populations.
What is the experience in New Zealand?
Wind farming is relatively new. Evidence from surveys measuring the impact of our first wind farms on bird and bat populations is starting to emerge. Although ongoing studies are required the early data is encouraging.
- The Brooklyn wind turbine is located on the outskirts of Wellington less than 20 metres from the Karori Wildlife Sanctuary. It has been operational for more than 10 years and in that time has received tens of thousands of visitors. Despite the proximity of the turbine to the wildlife sanctuary no native bird or bat mortalities have been reported since the turbine commenced operations in 1993. In the 10 years since the turbine first became operational the only fatality reported or known about, is one blackbird.
- Hau Nui wind farm has been operational since 1996. The turbine maintenance contract for this site requires the maintainer to monitor wildlife and avian deaths associated with the turbines. Since 1996 there have been no reported deaths.
- Tararua wind farm, in the Manawatu, has been running since 1999. If the turbines there had been killing significant numbers of native species substantial attention would have been drawn to the fact. Such attention does not exist and as a result there has been no formal study of bird impacts. Two or three years ago a Massey University student started a bird impact study. This was later abandoned in part due to lack of data.
- Documented collision rates in Australia are typically one or two birds per turbine per year and this number ties in with global recorded bird/ turbine impact rates.
How does mortality due to wind farms compare with other causes?
Birds are much more at risk from things that we take for granted, rather than wind turbines, as a result of our propensity to talk on cell phones, drive cars, live and work in tall buildings with windows and to keep pets (especially cats). The following numbers illustrate the point. A US study published in 2001 and carried out by Western Ecosystems Technology compares bird collisions with wind turbines against various other structures in the United States.
- Vehicles: 60 million to 80 million
- Buildings and windows: 98 million - 980 million
- Powerlines: tens of thousands - 174 million
- Communications towers: 4 million - 50 million
- Wind generation facilities: 10,000 - 40,000
The study estimates that wind farms kill an average of 2.9 birds per turbine per year in the United States. This is equivalent to less than 0.02 per cent of the 200-500 million collision related deaths that currently occur every year in that country. This estimate includes the fatalities at wind facilities such as those in Altamont, California that were sited in an area of high avian usage and which have caused disproportionately high levels of bird mortality. It is also of note that this study does not give any consideration to the number of birds killed every year by cats. The well-respected Audubon Society in the US recently published a paper that estimated that every year one billion birds are killed by domestic and feral cats in the United States alone. As the domestic wind industry enters its next stage of development more and more information is coming to light that the avian mortality rates at New Zealand wind farms are lower than in the northern hemisphere. This appears to be due to the lack of large numbers of night-migrating songbirds in New Zealand. These occur in the Northern Hemisphere by the hundreds of millions and they make up about half of all the birds that collide with wind turbines.
Last updated: Tuesday, 24 October 2006
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