Avoidance and Displacement
The area of habitat destroyed for wind turbine construction is relatively small. However, if animals use less of, or completely avoid, the areas surrounding the turbine, it can lead to great habitat loss. Some scientists even suggest that such indirect effects at the population level can have a greater effect than direct mortality due to collisions.
In Austria, an extreme decline of the local black grouse (Tetrao tetrix) was observed after the construction of a wind farm–the population was documented¹. The wind farm is located directly on a lekking site which used to be used by 12 cocks, prior to construction. After that, the lekking site was abandoned by the black grouse for a period of 5 years. Over this 5 year period, the number of lekking black grouse went from 41 to 9 in the region around the wind farm¹. At the same wind farm, researchers found evidence for the decline of rock ptarmigan (Lagopus mutus).
Results from another study suggest that black grouse use the area less within a 500 meter radius of the wind turbine²'³.
A Spanish subspecies of the capercaillie, the Cantabrian Capercaillie (Tetrao urogallus cantabricus), was recorded far less after the construction of a wind farm, compared to before⁴. Signs of capercaillie were sought for (sightings, feces, feathers) both before and after the construction of the wind farm. One year after construction, significantly less evidence was found, suggesting a displacement of the animals from this area⁴.
In Sweden, after the construction of a wind turbine in close proximity to a capercaillie lekking site, a decline of 50% (from 10 to 5 cocks) was observed over a period of 5 years⁴. At the same wind farm, a capercaillie was found which had flown into the tower of a wind turbine⁵.
In two different studies on willow ptarmigan (Lagopus lagopus), conducted in in Scotland and Norway, no avoidance behavior was detected in the animals⁶'⁷.
Greater Prairie-Chickens & Greater Sage Grouse (North America)
Lekking site counts suggest that wind farms have an effect on greater prairie-chicken (Tympanuchus cupido) populations⁸. In the year prior to the building of the wind farms, 103 greater prairie-chickens were counted on 10 lekking sites in the surrounding area (88–1470 meters away). Four years after construction, only one lekking site was visited by just three individuals. In the fifth year, eight lekking sites were visitedby a total of 130 greater prairie-chickens. One of these lekking sites was located only 300 meters from the next wind turbine, possibly indicating habituation. Due to changes in other variables in the area during this time period (e.g. burning and grazing), it is difficult to say whether the construction of wind power facilities was the only cause of these fluctuations in population⁸.
In a study in Wyoming, USA, it was discovered that the chance of survival for greater sage grouse (Centrocercus urophasianus) was less in close proximity to wind turbines, compared to further away⁹.
On one wind farm in Kansas,wind turbines were found to have no effect on the brood success and nesting site selection of greater prairie-chickens (Tympanuchus cupido)¹⁰'¹¹. However, it could be demonstrated that female animals in the area changed their use of space, nevertheless. The home range of the birds after the construction of the wind farms was much larger than before the construction, and the birds preferred to use areas at greater distances from the turbines¹¹.
The afore-mentioned examples show the large variance in reactions among species and locations; however, what causes these differences is not clear.
It is known that many grouse species often collide with man-made structures in their habitats. Furthermore, it is already well-established that collisions with fences, electrical wires and ski lift cables often result in the death of many grouse.¹²'¹³'¹⁴'¹⁵
It is, therefore, not surprising that collisions with wind turbines should occur. In a Norwegian study, willow ptarmigan (Lagopus lagopus) were found to be the most common collision victims, with a total of 42 dead birds found⁷. Similarly, in Sweden there are instances of willow ptarmigan colliding with the towers of wind turbines¹⁶.
The following species of grouse are all known to have had fatal collisions with wind turbine towers:
- Sharp-tailed Grouse (Tympanuchus phasianellus) ¹⁷
- Willow Ptarmigan (Lagopus lagopus) ⁷'¹⁸
- Ruffed Grouse (Bonasa umbellus) ¹⁹
- Capercaillie (Tetrao urogallus) ⁵
- Black Grouse (Tetrao tetrix) ¹
However, the extent to which this additional mortality impacts the populations of these species is unknown. In species with higher life expectancies and relatively slow reproductive rates (i.e. grouse), an increase in the mortality rate of adults can have relatively quick negative impacts on their population²⁰.
Further Potential Influences
It seems that the construction of wind turbines has an influence on many grouse. What this influence is exactly, is unclear. It is evident that the birds are being disturbed during the building phase; however, the effects which may surface in the longer term are more complicated.
The size of modern wind turbines necessitates relatively large access routes. These must be either newly laid or replace already existing roads. Additional habitat is lost to the structural foundations and storage facilities of wind facilities.
If a wind turbine is built in grouse habitat, this inevitably leads to a loss of habitat. However, this likely only has significant effects on the population if the wind farms are very large or in very limited habitats.
Wind turbines produce noise of varying volume depending on the type, location and wind speed. It is unclear to what extent this influences grouse.
However,it is known that man-made noise can have an effect on the behavior of birds of other species²¹'²²'²³.
Shadows and Motion of the Rotor Blades
Rotor blade shadows move at different speeds on a daily basis, depending on the weather conditions and season. Similarly, the movement of the rotor blades themselves(also dependent on the weather and cloud conditions) are “abnormal” and unpredictable in the air.
Grouse react to shadows and motion in the air because they are prey to many raptors. It is possible that the movement of the shadows or rotor blades could cause a flight reaction in grouse, or disturb them. Grouse which live in open areas (e.g. the greater prairie-chicken) even avoid higher structures such as trees or power poles, likely because these structures are favored by birds of prey²⁴. However, for species which live in the forest, this reason is unlikely.
Most grouse species are very shy around humans. As such, an increase of humans in their habitats leads to a limitation in their habitat use. It is known that in areas with much winter tourism, capercaillie and black grouse have an elevated level of stress hormones compared to those in areas with fewer people²⁵'²⁶. Additionally, behavioral changes can be detected as a result of disturbances²⁶.
In addition, we know that capercaillie and black grouse avoid human hiking trails in many areas, and that this can lead to a limitation in habitat use.
New and rebuilt forest roads result, in many cases, in an increase in human use in those areas²⁷'²⁸. It is, therefore, accepted that the construction of roads for wind energy leads to a negative effect on grouse.
The above effects can impact grouse alone or in combination. As many grouse species are threatened and, therefore, under protection, these species will be accounted for in the planning and approval of wind turbines.
¹ Zeiler & Grünschachner-Berger (2009): Impact of wind power plants on black grouse, Lyrurus tetrix in Alpine regions
² Grünschachner-Berger & Kainer (2011): Birkhühner Tetrao tetrix (Linnaeus 1758): Ein Leben zwischen Windrädern und Schiliften
³ Zwart et al. (2015): Using environmental impact assessment and post-construction monitoring data to inform wind energy developments
⁴ González & Ena (2011): Cantabrian Capercaillie signs disappeared after a wind farm construction
⁵ Rönning: Tjäderkommittén
⁶ Pearce-Higgins et al. (2009): The distribution of breeding birds around upland wind farms
⁷ Bevanger (2011): Pre- and post-construction studies of conflicts between birds and wind turbines in coastal Norway (BirdWind)
⁸ Johnson & Young (2011): Greater Prairie Chicken Lek Surveys, Elk River Wind Farm, Butler County, Kansas
⁹ Johnson et al. (2012): Greater Sage-Grouse Habitat Use and Population Demographics at the Simpson Ridge Wind Resource Area, Carbon County, Wyoming
¹⁰ Mcnew et al. (2014): Effects of Wind Energy Development on Nesting Ecology of Greater Prairie-Chickens in Fragmented Grasslands
¹¹ Winder et al. (2014): Space use by female Greater Prairie-Chickens in response to wind energy development
¹² Catt et al. (1994): Collisions against Fences by woodland grouse in Scotland
¹³ Braines & Summers (1997): Assessment of bird collisions with deer fences in Scottish forests
¹⁴ Braines & Andrew (2003): Marking of deer fences to reduce frequency of collisions by woodland grouse
¹⁵ Bevanger & Brøseth (2004): Impact of power lines on bird mortality in a subalpine area
¹⁶ Falkdahlen et al. (2013): Fågelundersökning vid Storruns vindkraftanläggning, Jämtland
¹⁷ Brown & Hamilton (2004): Bird and Bat monitoring at the McBride Lake Wind Farm
¹⁸ Bioscan (2001): Novar Windfarm Ltd Ornithological Monitoring Studies - Breeding bird and birdstrike monitoring 2001 results and 5-year review
¹⁹ Kerns & Kerlinger (2004): A study of bird and bat collision fatalities at the Mountaineer Wind Energy Center, Tucker County, West Virginia: Annual report for 2003
²⁰ Sæther & Bakke (2000): Avian life history variation and contribution of demographic traits to the population growth rate
²¹ Brown (1990): Measuring the effect of aircraftnoise on sea birds
²² Slabbekoorn & Peet (2003): Birds sing at a higher pitch in urban noise
²³ Nemeth, E. & Brumm (2009): Blackbirds sing higher-pitched songs in citie: adaptation to habitat acoustics or side-effect of urbanization?
²⁴ Pruett et al. (2009): Avoidance Behavior by Prairie Grouse: Implications for Development of Wind Energy
²⁵ Thiel et al. (2008): Ski tourism affects habitat use and evokes a physiological stress response in capercaillie Tetrao urogallus: a new methodological approach
²⁶ Thiel et al. (2007): Effects of recreation and hunting on flushing distance of capercaillie
²⁷ Forman & Alexander (1998): Roads and their major ecological effects
²⁸ Summers et al. (2007): Measuring avoidance by Capercaillie Tetrao urogallus of woodlands close to tracks