A new study has shed light on how offshore wind turbines and marine infrastructure may threaten millions of migrating birds crossing open ocean routes in North America. Using radar data from U.S. coastal weather stations, researchers found that songbirds migrate over narrow windows of time in spring and fall, flying at lower altitudes than they do over land sometimes within the height range of turbine blades.
The study, published in the Journal of Applied Ecology analyzed radar data from 16 weather stations between 2014 and 2023. It revealed that 20–40% of bird traffic occurs below 300 meters the height range of many offshore turbines suggesting that collisions could be a real risk. However, scientists say this danger can be reduced with “dynamic management,” meaning wind farms could temporarily pause operations during peak migration nights.
Lead author Shannon Curley, a movement ecologist at the Cornell Lab of Ornithology, explained that birds tend to migrate over the sea during calm weather when winds are most favorable. This natural timing could make it easier for wind farm operators to adjust turbine activity without significant energy loss.
The study also found that migration over water happens in fewer nights compared to over land with 90% of bird traffic occurring over just 36 nights at sea during spring and 37 nights in fall. This concentration could help managers better predict when to take action.
Researchers hope to develop forecasting tools similar to BirdCast currently used for land migration to predict offshore bird activity in real time. Such systems could guide not only wind energy projects but also offshore oil and gas operations to reduce bird mortality.
While wind turbines cause hundreds of thousands of bird deaths annually in the U.S., the study emphasizes that this number is small compared to other human impacts, such as domestic cats or building collisions. Still, as offshore development expands worldwide, experts urge balancing renewable energy growth with wildlife conservation.
Assistant professor Benjamin Van Doren from the University of Illinois said, “Songbirds migrating over inhospitable open water are already at high risk they can’t rest or refuel. It’s crucial that offshore projects minimize additional harm.”
Researchers believe that proactive planning and monitoring could make offshore renewable energy safer for wildlife while still supporting the transition to clean energy.