Avian radar technology is an important tool for assessing potential impacts of offshore wind farms to seabirds and migrating birds.
The Robin Radar MAX radar system deployed on Fedje in October 2022.
As the offshore wind energy industry grows to meet renewable energy targets, there will be an increasing need to ensure that we are monitoring and mitigating the impacts to birds at sea. One of the aims of the MARCIS project is to develop novel methods for monitoring bird movement and behaviour at offshore wind farms. We will develop these methods for monitoring birds crossing Hywind Tampen, the world’s largest floating offshore wind farm which is being installed in the North Sea.
Monitoring bird activity in offshore energy sites can be challenging given their distance from shore and the changeable weather conditions. Telemetry methods, like GPS tracking, can provide information about how individual birds use an area, but they are expensive and limited to tracking a relatively small number of birds. Geolocators are cheaper and lighter, but unfortunately do not provide the resolution needed to monitor bird movements around a wind farm site.
Radar technology provides an interesting solution for monitoring large numbers of birds passing a site over a long period. Radars have successfully been used to monitor bird activity at airports for decades, and long-range weather radar systems have recently been used to reveal patterns of large-scale bird migration in the Netherlands and the USA. For example, models developed by Cornell Lab of Ornithology have detected hundreds of millions of birds crossing the USA on a single night, using data from the US weather surveillance radar network. Recent technology developments have resulted in purpose-built avian radar systems that can monitor bird activity at almost any site, including around energy installations like wind farms. These new radar systems track birds in 3D at distances of up to 10km and altitudes of up to 3.5km, although the likelihood of the radar detecting a bird will decrease with distance from the radar and size of the bird.
Dokter, A. M. 2022. BirdCast, live migration map; 04/11/2022 23:30 ET. Cornell Lab of Ornithology. birdcast.info/live-migration-maps
Radars work by sending out a transmitting beam which reflects off objects, like a plane or bird. The reflected wave is then received by the radar system and a measurement of the size, speed, direction and altitude is made. The radar rotates at a speed of about 1 second per rotation, and repeated measurements of the object allow us to track it in real time. Software can then be used to identify the type of object based on size, such as small, medium or large birds, flocks of birds, aircrafts or vehicles.
A 3D avian radar system has been installed on one of the turbines at Hywind Tampen, and we will soon start to receive data from the system. In order to be able to identify which bird species are detected by the radar we will develop a model that can identify the type of species based on the characteristics of their radar track e.g., the speed, altitude and turning angles.
Before a model can be developed and validated, we first needed to collect ground-truthing data of radar tracks. A pilot radar study was completed in October/November 2022 on the island of Fedje, off the coast of Western Norway. Ground-truthing involves an observer identifying the species that corresponds to a radar track and labelling it in real-time. This generates a dataset of radar tracks where we know the bird species that corresponds to each track – from this we can then build the models for analysing data collected from Hywind Tampen. At Fedje we observed resident birds, like herring gulls, great black-backed gulls, cormorants, shags and white-tailed eagles foraging along the coast, as well as migrating birds passing the island further offshore. Some of the migrating species included gannets, eiders and guillemots. During nights with calm weather conditions large numbers of birds were detected flying over the island at a rate of thousands of birds passing per hour. Many of these were songbirds, such as redwings and blackbirds.
Bird tracks detected by the MAX radar on Fedje, showing both local bird movements (right) and possible migration movements (left); Yellow, orange and red tracks represent small, medium and large birds, respectively, pink tracks indicate likely flocks
This research will give us much better insights into how birds behave around wind farms, and how this varies by species. For example, whether birds are attracted to or avoid wind farms has a large influence on their risk of collision with a wind turbine. The data we collect will allow us to track bird movements around the turbines themselves – we can measure what height they fly at, how close they get to the blades etc. We will also be able to track large migration movements through Hywind Tampen and gain a better understanding of the favourable environmental conditions and timing of migration in that area.
The results from this part of the MARCIS project may help to inform the placement of future offshore wind farms, reducing the number of bird collisions and the overall environmental impacts from offshore wind turbines.