Abstract
During the execution of the project Development of instruments for a nature-inclusive energy transition (KB-36-003-002) in August-September 2018 and 2019, common noctules Nyctalus noctula were equipped with multiple tags to calibrate a triangulation algorithm for the Dutch Motus network (Lagerveld et al in prep). This algorithm is needed to derive flight paths based on received signals from the Motus receivers. The tagged individuals were equipped with a GPS tag to obtain accurate location fixes, a coded (Motus) VHF tag to obtain simultaneous detections at one or more Motus receivers, and a VHF beeper tag to ensure relocation of the tagged animal, or to find the fallen-off tag-pack in the field.
From this study we learned that some of the nocturnal feeding trips of these common noctules took place above coastal North Sea waters, up to 12.7 km offshore in the end of August 2019 (Lagerveld et al in prep). This was the first evidence that at least some local, non-migrating bats venture out offshore during nightly foraging trips in Dutch waters, thus theoretically becoming vulnerable to adverse effects from operational offshore windfarms. This could be even more hazardous taking into account that common noctules fly relatively high, in general well within the rotor swept area (RSA).
Given the observations described, Rijkswaterstaat felt the need to carry out a pilot study within the Offshore Wind Ecological Programme (WOZEP) in order to assess the importance of the maritime habitat for local common noctules living in coastal colonies in more detail.