Minimizing aviation lighting duration reduces bat attraction to wind turbines

Abstract

Wind turbines negatively affect bats through mortality, which can be exacerbated by attraction behaviours, and loss of habitat use caused by avoidance behaviours. However, potential mechanisms driving bat responses to wind turbines are still poorly understood. This is especially true of red aviation lighting, designed to prevent aircraft collisions and implemented in many countries, that could be perceived by bats from a long distance and lead to a response at a large spatial scale. We assessed the role of wind turbine red aviation lighting in the behavioural responses (attraction and avoidance) of bats. To this end, we acoustically quantified the activity of three functional bat guilds (long-, medium- and short-range echolocators) at three wind farms using a triplet sampling design: recordings were conducted simultaneously at (i) wind turbines illuminated throughout the night, (ii) wind turbines equipped with the aircraft detection lighting system (ADLS) and illuminated an average of 12% of the night and (iii) control sites without nearby wind turbine. Thirteen and nine triplets were sampled at wooded edges ~250 m from the nearest wind turbine and in open habitats at the base of the turbine, respectively, during two consecutive nights in June 2021 in the Uckermark district (north-east Germany). We found that acoustic activity was higher overall at sites near wind turbines illuminated throughout the night than at control sites for all functional guilds and both at wooded edges and in open habitats, indicating local attraction behaviours towards wind turbines that might increase collision risks. Activity at sites near wind turbines with ADLS was lower overall than at sites near wind turbines illuminated throughout the night, and similar to control sites, suggesting that part-night lighting could contribute to reducing bat attraction towards wind turbines. Synthesis and applications. This study provides empirical evidence that attraction behaviour of bats towards wind turbines is driven, at least partially, by red aviation lighting. We also demonstrate that smart lighting of wind turbines, such as the ADLS, could cost-effectively help mitigate disruption of bat habitat use and the associated collision risks. Implementing adaptive lighting strategies could therefore represent a practical step towards balancing wind energy development with bat conservation.