Birds and wind farms

The Swiss Ornithological Institute evaluates technical developments with respect to possible consequences for birds. Wind farms are currently being promoted because they do not emit CO2. From a bird conservation point of view, the use of wind power may pose serious problems, however.

Aims

The Swiss Ornithological Institute analyses scientific studies dealing with the consequences that wind farms may have on birds. The Institute evaluates the locations of planned or potential wind farms in Switzerland in relation to the possible consequences on birds. The primary questions addressed are:

a) What is known about the consequences of wind farms on birds?
b) What are the expected consequences of wind farms on birds in Switzerland?
c) How can negative consequences of wind farms on birds in Switzerland be mitigated or avoided?

Significance

In Switzerland, the use of wind power is in its infancy. According to official declarations, however, the use of wind power should be increasingly expanded until 2010. To avoid detrimental effects on nature and wildlife, in particular birds, negative consequences should be known and avoided in the planning of projects to make them as "bird-friendly" as possible. A review conducted by the Swiss Ornithological Institute provides relevant guidelines.

Results

Are wind farms "bird-friendly"? The answer is: not always. Negative impacts of wind farms on birds have been documented in several studies. The main risks are collisions of birds with wind turbines and effects on habitats and on the behaviour of birds. Collisions with wind turbines primarily concern migratory species and large birds like soaring raptors or storks. Birds can a) collide with the rotor blades or with the masts of wind farms, b) get into the suction of the turbines or c) be smashed to the ground by turbulences. Therefore, wind farms should not be constructed in places where birds assemble or migrate due to favourable thermal or topographic conditions (e.g. mountain passes, banks along large water bodies, etc.).

Masts measuring wind speed are secured by several tensioning wire ropes. It is known that birds collide with such wire ropes as well as with aerial lines leading the energy gained away from wind farms.

Birds are mobile and make wide use of suited landscapes. Wind farms and associated infrastructure can substantially lower the quality of habitats. Several reviews have shown that birds use areas with wind farms either less or not at all compared to areas without such structures. Furthermore, areas with wind farms may still be used, but birds appear to be more agitated and to fly off more often than in areas without wind farms. Such stress situations may physically weaken migrating or overwintering birds and potentially reduce their survival chances. For breeding birds, stress situations often result in lowered reproductive success, which may lead to local declines of populations. Other bird species may continue to use an area in much the same way as before the construction of a wind farm. For example, many birds occupy the same area over many years, regardless of an apparently reduced habitat quality due to the wind farm. However, it is unclear whether or not new individuals settle, if habitat quality has been reduced to strongly.

The development of so far little used landscapes may lead to changes in the agricultural practices or to an increased number of visitors. As a consequence, disturbance-sensitive species such as the highly endangered capercaillie may abandon newly developed areas.