Collision risk for migratory birds

Fixed Pencil Beam - Radar during construction
Fixed Pencil Beam - Radar during construction

IfAÖ Institut für Angewandte Ökosystemforschung GmbH

In the spring and autumn of each year, several million birds complete the journey between their breeding grounds and winter quarters, crossing the North Sea and Baltic Sea. Offshore wind farms might be particularly prejudicial to night-time bird migration, in the light of phototactic attraction and the increased risk of collision. It is conceivable that, under favourable migratory conditions (clear visibility, following wind) migrating birds might be able to complete their passage whilst avoiding wind farms; however, in poor weather (sea mist, precipitation, headwind), they might be attracted at night by the brightly-lit turbines and exposed to an increased risk of collision.

In order to evaluate the risk of collision for migrating birds, migration patterns in the vicinity of existing installations must be accurately quantified and compared with conditions where no disturbance is present. To this end, Fixed Pencil Beam Radar has been developed for the quantification of bird migration and installed on the FINO1 research platform in the vicinity of “Alpha Ventus”, the first North Sea wind farm. By the tight concentration and focus of the radar beam, the volume of samples for the calculation of rates of migration can be accurately defined, and the probability of data capture, particularly for low-flying birds, will be superior to that obtained using a conventional ship’s radar. Echo signatures from the radar display should also allow an automatic distinction between birds and other objects, together with the subdivision of birds into categories. In this way, migration patterns can be accurately plotted, specifically in the hazardous zone of a wind farm. The measuring system is designed for the alternating measurement of migration both inside and outside the “Alpha Ventus” wind farm at various altitudes, in order to allow the appraisal of potential evasive movement and/or the attraction of birds under various weather conditions.

In tandem with radar measurements, bird movements in the vicinity of a wind turbine are plotted using a night vision camera, in order to allow the documentation of potential collisions.