Directorate Natural Environment
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Biodiversity: Sea Birds and Bats
Research is being carried out using a bird radar to study the effect of offshore wind farms on birds, in addition to the monthly counts from ships carried out by the INBO (Research Institute for Nature and Forest). This bird radar is installed on a platform in the C-Power wind farm on the Thornton Bank, about 25 km offshore.
The system consists of a vertical and horizontal aerial. Every time these aerials rotate, radar energy is emitted. When this energy hits an object it is reflected back and received by the aerials. This reflected signal gives information about the object it struck. As this research is interested only in birds, software has been developed to distinguish birds from other objects in the environment.
The vertical radar aerial collects data on the number of birds flying through the area and at what height. This vertical radar has a reach 3.6 km wide and 3.6 km high. On the basis of these data and mathematical models an estimate is made of the number of birds that collide with the wind turbines. The horizontal radar records the flight movements of the birds within a radius of almost 8 km. These data therefore provide information on the flight direction and flight path taken by the birds. A change to their flight path can indicate that they are aware of the wind farm as a barrier and have changed direction accordingly.
The big advantage of this installation is that it provides continuous data on the presence of birds. Data can therefore be collected on the number of birds that fly over the sea at night during migration. The disadvantage of the bird radar is that the data do not distinguish and record the bird species encountered. In this sense, the radar research and bird counts carried out by the INBO are complementary.
We know that some species of bat fly great distances during their migration from their wintering areas to reproduction areas and back again. Sometimes this involves flying over the sea. In recent years there have been many observations of bats on oil platforms and at offshore wind farms. Due to the (planned) construction of a number of wind farms and recent observations in the Netherlands of the presence of bats at offshore wind farms, there are now growing concerns about the possible effects of offshore wind turbines on this vulnerable group of mammals.
Until recently there had been no systematic research into the presence of bats over the Belgian section of the North Sea. In the autumn of 2014 an automatic bat detector was fitted to the research vessel RV Belgica, in order to carry out initial research into the presence of bats over the sea and into the species concerned. Only a part of these data have been processed to date but various species of bat have been identified already: Nathusius' pipistrelle, common noctule, Daubenton’s bat and the rare particoloured bat. Most recordings were made within 5 km of the coast, although some were made 20 km from the coast.
Also in the autumn of 2014, as part of the Lifewatch project, an automatic detector was fitted to an offshore wind turbine. The combination of data collected by these two detectors (and possibly more in the future) will allow us to gain an idea of how wind turbine farms affect bats. It will be important to learn whether or not bats are attracted to wind turbine farms, how they behave close to wind turbines and the numbers that collide with the turbines.
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