This report presents data on infrared monitoring investigations by use of Thermal Animal Detection System (TADS) of migrating waterbirds at the Nysted offshore wind farm, Denmark.
Information presented covers the autumn period of 2003 and spring period of 2004.
The aims of the report were threefold:
- to present preliminary data on the number of avian collisions using infrared video recording (TADS),
- to assess the performance of the TADS during prolonged operation in an offshore environment,
- to amass information (data collected by radar) to model the probability of birds passing the sweep area of offshore wind turbines (Appendix I) in order to present recommendations for the development of a future TADS-study to be conducted from autumn 2004 onwards.
During operation the thermal trigger software saved 1,223 thermal video sequences on hard disc (see Table 1), of which only three were triggered by birds passing the field of view all in a 45° viewing mode. No birds were recorded as passing the sweep area of the rotating turbine blades nor colliding with any part of the turbine during the 11,284 minutes of monitoring.
The final quality control of the offshore utility of the TADS produced excellent results. It can be concluded that TADS can be considered as a fully developed monitoring set-up capable of detecting migrating birds flying over offshore areas and passing at the range of distances planned for the equipment.
The fact that no birds were recorded as passing the sweep area of the A2-turbine could give rise to some doubt as to whether the TADS actually functioned properly during the trial. However, comparison with data gathered from other sources confirm the extremely low intensity of waterbird migration in the near vicinity of the turbines:
- the 5-min long manual sequences of horizontal view successfully detected 52 birds despite the very restricted number of operation hours,
- the radar data on bird flocks migrating within the wind farm show significant avoidance responses towards individual turbines, resulting in a higher probability of flying more than 50 m from the turbines than expected by chance alone.
Given the maximum coverage of c. 30% of the sweep area per TADS and the monitoring efficiency of 63.7% during the study period, it is considered highly unlikely that the single TADS used in the present study would have detected the single theoretically estimated flock of Common Eiders forecast by the probability model (Appendix I) to be crossing the sweep area of a single turbine.
As a consequence of the extremely low estimated probability of Common Eiders passing the sweep area of the turbines (Appendix I), the level of coverage required to adequately monitor all 72 turbines would be extremely high, if a realistic and reliable measure of the daily number of avian collisions are to be registered by use of TADS only. Hence, it is considered that using TADS as the only method to measure actual collision rates of Common Eiders at the Nysted Wind farm is neither an economical nor practical option when it comes to estimation of the daily low number of collisions.
NERI therefore proposes future collision studies to include a combination of data collected by radar and TADS for use as input to a more accurate and statistically robust model of the probability of daily number of avian collisions.
Finally, a monitoring programme with TADS at a relatively low intensity (i.e. one TADS) could, besides collecting data for the probability model, function as a background monitoring scheme, aiming at detecting periods with high number of collision casualties under rare and unusual situations, which in contrast to the low daily collision frequency do not need any intensive coverage.