Batmobile - Impact of offshore wind farms on bats in the German Bight and the Baltic

The project aims to identify factors that increase the risk of collision and mortality for bats with offshore wind turbines. It is to be examined to what extent areas in which bats congregate such as flight corridors exist that could be used as a basis for impact reducing spatial planning measures and whether behavioural patterns (such as exploratory behaviour of man-made vertical structures) exist that could significantly increase the risk of collision. On this basis, standard methods for the impact assessment of offshore wind farm projects for bats are to be formulated as a basis for an updating of the federal approval concepts.

Methods

Within the framework of Batmobil it is planned to

• establish potential areas of dense bat populations via bio-acoustic investigations,
• determine individual flight routes using telemetric methods, and
• behavioural investigations during flight and at vertical (man-made) structures.

The following questions are to be addressed:

• For bats, are there offshore sites of concentration, area-centred populations or flight corridors? In any way, sites with increased occurrence probabilities of migratory bats represent sites with increased conflict potential.
• What flight behaviour do migratory bats show over the sea? What flight routes and flight altitudes do they use? Specific flight routes can provide additional information on the existence of densely populated sites. Again, flight altitudes within the reach off the rotors of offshore wind turbine have significant influence on collision risks.
• How do bats migrating over the sea behave at vertical structures such as offshore wind turbines? Do they change flight altitude? Do they show exploratory behaviour? Due to certain behaviours (such as the exploratory behaviour at offshore wind turbines) the collision risk may be significantly increased.

On that basis, standard methods for primary surveys and monitoring of bats at specific wind farm projects are to be developed and formulated. These can be directly integrated into the standard survey concepts of the federal approval authorities.