Figure 24: Distribution and migration of Nathusius’ pipistrelle.
Threats to migration pathways The main threat to Nathusius’ pipistrelles is the loss of habitat due to forest practices that do not take account of bat needs. The felling of trees with cavities, especially in riverine woodlands, and the drainage of wetlands can affect both breeding and wintering populations. The availability of suitable roosts along their migration paths is also vital for the species. Nathusius’ pipistrelle is increasingly faced with a new threat: wind turbines. Bats are known to be particularly sensitive to wind turbines. They can be fatally injured if they enter the pressure zone around the spinning blades of the turbine, suffering from a collapse of the lungs and internal organs known as “barotrauma”. The increasing development of wind farms along migration routes in coastal areas, in mating areas, and in wetlands where the pipistrelle hibernates, has revealed that mortality as a result of collision with wind turbines or barotrauma is high. The bats
appear to be attracted to wind turbines operating at low wind speeds, possibly because of insects collecting above the turbine which the bats feed on. During the last few decades many onshore and offshore wind farms have been built along these routes but the extent of the impact on Nathusius’ pipistrelle populations is still unknown.
Opportunities for ecological networks To protect Nathusius’ pipistrelle, the conservation and enhance- ment of wetlands and riverine forests with old trees is essential to allow bats to forage and mate along migration routes. The con- struction of wind turbines should be prohibited in these habitats or their use curtailed at night or during the migration period. Using higher cut-in speeds, i.e., the minimum wind speed at which the wind turbine will generate usable power, should also be considered in areas where threatened bats are present.