A study in southern Sweden (Ahlen, 2007) revealed that migrating bats regularly forage around the offshore wind turbines because of the accumulation of flying insects. In addition, non-migratory bats used the wind farms as a foraging area.
In the past decades there have been several records of bats found on oil platforms in the Southern North Sea (Bekker & Boshamer, 2008, Russ (2000), Skiba (2007) Walter (2007)) and some offshore sightings of bats during bird surveys at sea (personal observation SL & HV). The presence of bats in the Southern North Sea however has never been investigated systematically. Therefore it is not known if these records refer to regular migrants, stragglers who got lost or blown off course during migration, or even animals that use the North Sea as a foraging area. If and how offshore wind farms in the North Sea are used by bats is a relevant question for policy makers and wind farm developers, considering that the number of offshore wind farms in the North Sea will be increasing and that several (onshore) studies have shown that wind turbines can cause high fatality rates amongst bats. For all wind farms in Germany combined Voigt (2012) estimated approximately 200.000 bat fatalities each year.
The Fieldwork Company and IMARES Wageningen UR have joined forces to carry out a pilot study on bat activity in wind farms in the Dutch part of the North Sea. NUON and ENECO contributed by giving their permission and cooperation to install ultrasonic recorders in their offshore wind farms ‘Offshore Wind farm Egmond aan Zee (OWEZ)’ and ‘Prinses Amalia Windpark (PAWP)’. The main objective of this pilot study is to assess whether bats are present in the two Dutch offshore wind farms, as well as to assess the feasibility of ultrasonic bat recorders under offshore circumstances on the North Sea. An additional objective was to see whether indications for bat migration could be found in the recorded data.