A study focusing on three wind turbines in the Jura mountains in western Switzerland has shown that on average each one causes the death of 14 to 29 birds a year – almost triple previous estimates. Migration periods were associated with more deaths but visibility could also play a role.
Small, nocturnal migratory birds were the main victims, according to the study results – carried out by the Swiss Ornithological Institute for the Federal Office for the Environment – released on Monday. The study was the first of its kind to combine counting bird carcasses while also monitoring bird passage using a radar device.
A total of 51 bird remains were found around the turbines of which 20 were classified as killed in collision with the turbine blades at the Le Peuchapatte site. Taking into account search efficiency and the probability of finding the bird carcasses in the search area, the actual figure could vary between 43-89 victims. The study suggests that weather could be a factor influencing bird collision rates.
“Even though most ‘collision events’ took place during the migration period in spring and autumn, the highest number of deaths did not take place during peak migration intensity. This suggests that other factors may also play a role and one such factor could be visibility,” Michael Schaad of the Swiss Ornithological Institute told swissinfo.ch.
Not so clean energy
According to the researchers, the 14-29 bird collisions per turbine per year is a conservative estimate.
However, the generally accepted benchmark used to assess the impact of the wind power stands at ten birds per turbine per year, suggesting a significant underestimation. The results of the study cannot be extrapolated to other parts of the country like the Alps or the plateau but are relevant for areas that are topographically similar with similar wind turbine sizes and heights.
The new Energy Strategy 2050 unveiled by the Swiss government foresees a production boost of renewable resources to 11.4 terawatt-hours by 2035, nearly four times the current output. To help investment in renewable energy resources, including wind power, parliament has decided to ease regulations for the construction of power plants in nature reserves. Not everyone is happy about the development.
“Wind energy is the only one that has a direct impact on birds. But indirect impacts like loss of habitat and disturbance due to construction have a greater impact than collisions and hence choosing the site for wind turbines is very important,” says Schaad.