How many birds are killed by offshore wind turbines? Scientists use thermal cameras to find out

Europe leads the world in offshore wind energy, with more than 30 gigawatts (GW) of installed capacity across the continent – enough to power more than 26 million homes annually. ADVERTISEMENT ADVERTISEMENT Earlier this year, Belgium, Denmark, France, Germany, Iceland, Ireland, Luxembourg, the Netherlands, Norway and the UK committed to deliver 100GW of joint offshore wind projects across shared North Sea waters by 2050. The €9.5 billion plan, known as the Hamburg Declaration, aims to turn the North Sea into the world’s “largest clean energy reservoir” and mobilise €1 trillion of capital in Europe. But is our path to a fossil fuel-free future jeopardising birds that are already plummeting in number due to human-caused climate change? Are offshore wind turbines a threat to birds? Most studies into bird collisions with turbines tend to focus on wind farms located on land. But every year, millions of songbirds cross the North Sea during spring and autumn migration, mostly at night. Capturing collisions at sea can be difficult, due to a lack of light and the remote location. However, a new year-long pilot study has allowed researchers to detect these small birds and bats during hours of darkness, as well as larger birds during daylight hours, using a combination of thermal cameras and artificial intelligence (AI). The study, initiated by the energy company Vattenfall, was carried out at the Hollandse Kust Zuid offshore wind farm in collaboration with Wildlife Imaging Systems (WIS) and Wageningen University & Research (WUR). WIS installed 16 thermal cameras on an offshore wind turbine, covering all angles and operating 24 hours a day. Combined with AI, the system detected and interpreted bird movements day and night, including in poor visibility such as fog or rain. “Safeguarding biodiversity is an important part of the energy transition,” says Karen Krijgsveld, a bird ecology researcher at Wageningen University & Research. “On land, we already know quite a lot about when and why birds collide with turbines, and which species are most at risk. As offshore wind energy continues to expand, we need to develop that same understanding at sea.” Over almost a year of monitoring, covering both a spring and an autumn migration season, 22 possible bird collisions were identified – two of which were confirmed and one considered highly probable. “Until now, estimates of offshore bird collisions were mainly based on theoretical models,” says Jesper Kyed Larsen, a bioscience expert at Vattenfall. “At sea, it’s extremely difficult to verify fatalities because there are no remains to recover. This study demonstrates how we can get the empirical data needed to improve collision estimates and secure efficient mitigation measures.” The study does not claim that collisions are rare or that these initial results from one turbine can be applied everywhere. The primary aim was to test the technology’s performance under real offshore conditions. But a previous study by the German Offshore Wind Energy Association (BWO) also yielded similar results. Researchers analysed more than four million bird movements over one and a half years, using radar and AI-based cameras. They found that more than 99.8 per cent of migratory birds reliably avoided the wind turbines. Vattenfall previously conducted another study on an offshore wind farm near Aberdeen, Scotland. Over a period of 19 months – from June 2023 to December 2024 – video recordings of a wind turbine were made with the help of AI-supported analyses. A total of 2,007 bird flight paths near the monitored turbine were examined and no collisions were found. How can Europe protect its endangered birds? Despite all three studies suggesting a minimal impact of offshore wind farms on birds, conservationists warn that measures must still be put in place to help protect endangered species. Of the 26 seabirds that breed on the UK’s coastlines and islands, 10 are already on the endangered list. Back in 2020, the land-based Smola wind farm in Norway, which consists of 68 turbines, painted one blade on each turbine black to make them stand out to birds. They found the initiative reduced avian fatalities by a staggering 70 per cent, from 11 recorded bird carcasses before painting to six afterwards. Some critics argue that making wind farms more visible could impact birds’ migration patterns, forcing them to fly longer routes around a turbine. This means they will use up more energy, and it will take them longer to get back to their chicks. Other measures include placing turbines far away from sensitive habitats and avoiding migration paths in the first place. Thermal cameras and radar can also be used to further investigate the risk these turbines pose to our flying friends.