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Balance on the Horizon: An Analysis of the Impacts of Wind Power Production on Native Birds and Bats in New Zealand

By Raquel Crosier

NZ Wind

Image 1. Project West Wind (Phelps, 2011)

Wind Energy Development in New Zealand

During the past couple of decades, the development of wind energy in New Zealand has been on the rise. Wind energy was introduced in New Zealand in 1993 and now makes up 4.5% of the country’s energy portfolio (Bridges, 2013). While wind power is recognised as one of the greenest forms of renewable energy, no form of energy production is without environmental effects. Construction and ongoing operation of wind farms has both direct and indirect impacts on birds, bats and other wildlife. Unfortunately, the extent of the environmental impacts is often realised after the damage has been done.

There are various threats to New Zealand’s indigenous birds; pressures from human development, non-native predators and habitat reduction. Reducing threats and recovering native bird populations is a primary focus of conservation efforts in New Zealand.  While the impact of wind energy on birds has been heavily studied in parts of the world, very little research has been done on the impact of wind energy on native birds in New Zealand. Utilisng existing international research on the impact of wind energy on birds, this paper aims to identify risk factors for avian species, discuss the implications for specific species in New Zealand and presents some tools to minimise the impacts of wind development on native birds and bats.

Impact of Wind Farms on Native Birds and Bats

Good quality landscapes for wind development can often overlap with good quality habitat for native birds and bats. Wind farms need open landscapes with high wind speeds to be successful. Common areas for siting wind farms include hillsides, coastlines and offshore areas. When the landscape is shared by both birds and wind turbines, it is common to see increased avian mortality rates due to collision, changes in migratory patterns and diminished habitat value due to construction. Activities associated with the construction of wind farms (movement of equipment across the landscape, erection of turbines, building transmission towers, etc.) can cause soil disturbance, impact native flora and habitat quality, and displace native species. Habitat degradation and displacement are harder to measure but may be equally destructive to native bird and bat populations as turbine collision.


Image 2. Raptor killed by wind turbine  (Delingpole, 2013)












According to a recent study, 234,000 birds die per year in the United States from collision with wind turbines (Loss et al, 2013). An annual collision fatality figure has yet to be estimated for New Zealand, and cannot be calculated until all wind facilities are required to collect data on annual collision fatality rates. So far, only one wind facility in New Zealand has conducted a post-construction collision study, the West Wind Project. The West Wind study found that the facility had an annual mortality rate of 363 birds, and that one native species was significantly at risk of collision fatality, the Australasian harrier (Circus approximans) (Bull, 2013). The Australasian harrier fly at high altitudes and use thermal winds to hunt for grassland prey, which may put the species at risk of collision with wind turbines (Hutching, 2012).

Certain species have an increased risk of collision due to their geographic range, flight patterns, breeding and feeding needs. Some of the features that put avian species at risk are; high flight time, low manoeuvrability, poor eyesight, nocturnal flight activity, and nesting, rearing or migrating near a wind farm (Garthe and Huppop, 2004). These features, when paired with low reproductive rates and/or slow rate of sexual maturity can make a species particularly vulnerable to population decline in response to wind farm development. With these risk factors in mind, we will now consider which New Zealand bird and bat species may be at higher risk of collision.

Species at Risk

Although there is not any offshore wind in New Zealand, the country does have a few wind farms that are located right along the coastline. Due to their distribution patters, nesting and feeding habits, coastal wind farms can put some seabirds at risk of turbine collision or displacement. The Hutton’s shearwater (Puffinus huttoni), a nationally endangered New Zealand seabird, spends the day fishing and foraging on the coast, then flies inland at night back to their breeding colony in the Kaikoura Range (Cuthbert & Davis, 2002).  Due to nocturnal flight activity and high flight time, high risk of collision would be expected if wind turbines were present in their migratory range.  Development of wind sites within the range of a species such as the Hutton’s shearwater, with a slow reproductive rate, could have devastating impacts on an already declining population (Powlesland, 2009).

Another group at risk of collision with wind turbines due to their nocturnal flight activity are bats. Environmental monitoring of wind farms in the US has found that wind production has significant impacts on North American insectivorous bats. Injury and mortality of these bats is being caused by collisions with the fast moving blades of the wind turbines (Kunz, 2007). Researchers are unsure why bats are drawn into turbine blades, though there are a number of hypotheses. One is that bats are drawn to wind farms due to increases in the density of aerial insects after disturbance associated with construction (Kunz, 2007). Another hypothesis is that bats are drawn to the sound made by the wind turbines, which is the same low-frequency as that of chorusing frogs and insects (Buchler and Childs, 1981). Bats use this low frequency sound to locate food. Other reasons for the collisions may include; failure of bat echolocation to pick up moving turbines, fog and rain limiting visibility, and disorientation due to wind vortices caused by turbines (Kunz, 2007).

This research on North American bats has some serious implications for bats in New Zealand. The NZ long-tailed bat is an aerial insectivore which can fly as fast as 60km/hr and has a large range of up to 100 km.  Aerial feeding, roosting habitat and fast flight puts this species at risk of collision with wind turbines. If a wind farm were located near the roosting forest habitat of long-tailed bats, which are primarily on the South Island, it would put this threatened species at significant risk of collision with turbine blades (DOC, 2014).

Studies of turbine collisions in California in the United States have found that raptors had the most collision related mortalities (Kingsley and Whittam, 2005). Raptors are vulnerable because they fly at high altitudes and prefer windy ridgetops and slopes to soar and stalk prey. Their preferred habitat can often overlap with desirable wind development areas.  The  Morepork (Ninox novaeseelandiae), may be one species of raptor that is particularly at-risk due to their flight patterns, nocturnal flight activities, roosting habitat and sensitivity to light. Lights on wind turbines illuminate the structures to keep them visible to planes but can distract nocturnal birds which are sensitive to light, increasing their risk of collision (Powlesland, 2009).

Next Steps

Since wind development is still fairly new  to New Zealand there is still a lot of work to be done in assessing the risk of wind farms on birds and bats, developing and testing tools to reduce those risks, and monitoring accumulative impacts by species. Outlined below are some suggestions for future research, monitoring and reporting as well as some tools for prioritisng wind site development.


Research should be conducted prior to construction and operation to determine species at risk, their distribution and their prevalence near existing and proposed wind farms. Research should also be conducted on ways to reduce the likelihood of collision, especially during the night and during inclement weather, when avian visibility is reduced. This could include painting patterns on turbine blades or adjusting lighting on turbines (Hodos, 2003).

Management Tools

In addition to research there are some management tools that could be adapted and employed to assist in the siting process for wind farms. Since good quality habitat for New Zealand’s native birds and attractive sites for wind development often overlap, the expansion of wind energy in New Zealand will depend on the ability to strike a balance between environmental and energy needs. An environmental impact assessment should be conducted and an associated map developed to identify areas not suitable for wind development due to habitat value or presence of threatened species. Environmental impact assessments are being used elsewhere at both the national and international level to determine the risk associated with land and offshore wind development (Fox 2006, Drewitt 2006)

The development and employment of a decision-making framework could assist managers in weighing the benefits and potential impacts of a proposed wind site. The framework should be based on various factors including; the presence of native wildlife, the conservation value of the species present, habitat quality, wind generation potential, etc. A decision-making framework could also help to prioritise the development of wind sites, giving preference to those sites with lower habitat value and some level of disturbance already (from grazing, agriculture, etc.).  In their 2013 study on New Zealand falcon and wind farms,  Searon and Barea proposed a decision framework specific to falcon but which could be broadened and used for other species (Figure 2 in appendix).

Monitoring and Reporting


Image 3. Wind Speed NZ (NIWA, 2014)

Information on avian impacts should be gathered through post-construction monitoring at all New Zealand wind farms for consistent national reporting on accumulative impacts on native species. The findings from the West Wind Project showed higher rates of mortality for Australasian Harrier, but despite this finding, no subsequent research has been conducted on the reasons for the higher collision rates. Post-construction monitoring should be required at all wind facilities and should be followed up by further research into the impacts on species found to be at higher risk of collision.

New Zealand has one of the highest capacity factors for wind (above 50%) and huge potential for further wind development (Huso, 2014). With the promise of further wind development in the decades to come, increased research into the impacts of wind farms on native birds and bats, as well as techniques to reduce collision and displacement of species, is prudent and should be a conservation priority.


  1. Simon Bridges. 2013. Speech to New Zealand Wind Energy Association. Beehive website. 21/3/2013.
  2. Allan L Drewitt et al. 2006. Assessing the impacts of wind farms on birds.  Ibis. Special Issue: Wind, Fire and Water: Renewable Energy and Birds. Vol 148, Pp 29–42, March 2006.
  3. Thomas H. Kunz, et al. 2007. Ecological impacts of wind energy development on bats: questions, research needs, and hypotheses. Frontiers in Ecology and the Environment 5: 315–324.[315:EIOWED]2.0.CO;2
  4. E.R. Buchler, S.B. Childs. Orientation to distant sounds by foraging big brown bats (Eptesicus fuscus). 1982. Animal BehaviourVo 29, Issue 2, Pp 428–432
  5. Thomas H. Kunz, et al.2007.  Ecological impacts of wind energy development on bats: questions, research needs, and hypotheses. Frontiers in Ecology and the Environment. Vol. 5, No. 6. Pp 315-324.;2
  6. Department of Conservation. 2014. Bats/ Pekapeka. Department of Conservation website.
  7. S.R. Loss, et al. 2013. Estimates of bird collision mortality at wind facilities in the contiguous United States. Journal of Biological Conservation. Vol. 168, December 2013. Pp201-109.
  8. Stefan Garthe and Ommo Huppop. 2004. Scaling possible adverse effects of marine wind farms on seabirds: developing and applying a vulnerability index.Journal of Applied Ecology. Vol 41, Issue 4, Pp 724–734.
  9. Ralph G Powlesland. 2009. Impacts of Wind Farms on Birds: a review. Science for Conservation 289. Department of Conservation. Pp 1-50.
  10. Kingsley, A.; Whittam, B. 2005. Wind turbines and birds. A background review for environmental assessment. Environment Canada. Canadian Wildlife Service, Quebec.
  11. Hodos, W. 2003. Minimization of motion smear :reducing avian collisions with wind turbines. NREL/R-500-33249 (unpublished)
  12. Cuthbert, R., & Davis, L. S. (2002). The breeding biology of Hutton’s Shearwater. Emu, 102(4), 323-329.
  13. Bull, L. S., Fuller, S., & Sim, D. 2013. Post-construction avian mortality monitoring at Project West Wind. New Zealand Journal of Zoology, 40(1), 28-46.
  14. Fox, AD et al. 2006. Information needs to support environmental impact assessment of the effects of European marine offshore wind farms on birds. IBIS. Vol 148, Issue Sup 1, Pp129–144.
  15. Hutching, Gerard. 2012.  Birds of prey – Australasian harrier, Te Ara – the Encyclopedia of New Zealand.
  16. Huso, Manuela. April 17th, 2014. Measuring and Mitigating Wildlife Fatality at Wind Power Facilities. Lecture for Victoria University Biological Sciences Department. Wellington, NZ.

Image 1. Phelps, Justin. 2011. Project West Wind. From the blog: Two Wind Farms Get New Zealand Closer to 90% Renewable Power.

Image 2.Delingpole, J. 2013. Raptor killed by wind turbine. From Wind industry big lies no 3: wind turbines are eco-friendly, The Telegraph.

Figure 1. R Seaton & LP Barea (2013) The New Zealand falcon and wind farms: a risk assessment framework, New Zealand Journal of Zoology, 40:1, 16-27.


Other Resources:

  1. Miskelly, C. M., Dowding, J. E., Elliott, G. P., Hitchmough, R. A., Powlesland, R. G., Robertson, H. A., & Taylor, G. A. (2008). Conservation status of New Zealand birds, 2008. Notornis, 55(3), 117-135.
  2. Allan L. Drewitt1 and Rowena H.W. Langston. 2008. Collision Effects of Wind-power Generators and Other Obstacles on Birds. Annals of the New YorkAcademy of Sciences. Vol 1134, The Year in Ecology and Conservation Biology. Pp 233–266, June 2008.




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