In recent years, research into the occurrence of bats at the Dutch North Sea has shown that there is regular seasonal migration over sea. However, so far, little is known about their migration ecology, the fatality risks at offshore wind turbines, and the number of individuals migrating over sea. Since the Dutch government wants to boost the further development of wind energy production in the southern North Sea, the Ministry of Economic Affairs commissioned to Rijkswaterstaat a Wind at Sea Ecological Programme (in Dutch: Wozep). This study, as part of the Wozep-project Behaviour and Collision Risk of Bats (Bats_2), investigates how telemetry can be applied to gain insight into migratory movements of bats over land and over sea and individual bat behaviour near and in offshore wind farms. To find out whether it is wise to continue and further develop telemetry research in the context of the Wozep programme, we first identified potential telemetry methods for small bats based on a desk study and selected the most promising method for the application of telemetry. Members of the team attended an international workshop on telemetry in Lund (Sweden) to gather practical technical knowledge, gain insight in data-management standards, and increase their international network. Several field tests were conducted to test the equipment and explore the possibilities of tracking. Finally, suitable locations for bat trapping in bat boxes and for the use of a Heligoland trap were identified.
In conclusion, we are confident that telemetry can be successfully applied to study migratory movements of bats over land and over sea and individual bat behaviour near and in offshore wind farms. Joining a wildlife tracking system like Motus (Canada) in order to enlarge the data collection, is highly recommended. Motus-members can get detections from both their own tags received by stations owned by other members, and from tags owned by other members if received by their own stations.