This report presents the work from a project that examined the ability and performance of remotely-operated techniques (such as radar) to observe the behaviour of birds when they are over the sea but near to the coast. The coastal and offshore waters of the UK are very important, on a world scale, for several species of birds. Large numbers of migratory birds use the airspace above these waters and the UK has obligations to protect these under international law and agreements. The advent of an ambitious offshore wind energy programme in the UK has underlined our current lack of knowledge of the species, number and distribution of birds at sea and their possible interactions with wind farms.
As part of the required Environmental Impact Assessments (EIAs) for offshore wind farms, the extent to which birds will encounter newly constructed developments has to be estimated in advance of construction. In addition, an assessment of likely collision rates with turbines requires basic data on bird numbers, flight height and flight behaviour, including knowledge of the birds’ abilities to avoid obstructions such as turbines.
The high costs and practical constraints associated with undertaking human observations makes automated remote sensing systems essential in order to gather enough data on the three-dimensional movement and volumes of birds moving through a proposed wind farm before and after construction. Nevertheless, some verification (by eye, or using acoustic equipment in conditions of darkness or poor visibility) of species and flock sizes is essential when analysing the information derived from remotely-operated equipment.
This study reviewed all potential applications of remote technologies, but specifically describes the ability of different radar systems to observe bird behaviour over the sea and the performance of the Thermal Animal Detection System (TADS) in detecting avoidance of turbines by birds and collisions between birds and turbines.
The study concluded that conventional marine ships’ navigation radar provides the simplest approach to the collection of data by tracking bird movements in two (horizontal) dimensions, throughout the day and night, to provide an overview of bird flight trajectories and hence movements within a proposed wind farm area. However, visual observations are essential to identify the species of birds involved. The report recommends the use of TADS to identify species and to measure flock size during poor visibility and during darkness. Vertically mounted radar can also provide information on the height of flying birds, although birds near the sea surface cannot be easily detected by such radar when the wind is strong enough to produce large wave reflections.
More sophisticated radar systems have been developed specifically to detect and track birds and automatically record data. These offer improved detection range and performance in a wider range of weather conditions, but the cost of such devices is ten times the cost of traditional ships’ navigational radar equipment.
Further improvements in the performance of radar techniques for monitoring the behaviour of birds are possible using available military technology. These include: increasing the bird detection range, improved detection of birds in rain, an increase in the ability to discriminate birds in space, identification of species, three-dimensional bird location and automated recording and statistical analysis. However, these improvements would increase the equipment cost still further.
The use of infrared imagery derived from TADS offers the best, if not the only, method of observing bird avoidance behaviours in close proximity to turbines and detecting actual collisions of birds with turbines. The method has been successfully tested in Denmark but has not so far detected any collisions during operations.
Other remote techniques are reviewed and discussed in the report, but few other methods are as useful, at present, as radar and TADS for these specific applications.