Every autumn, thousands of birds make their way across the Algarve, travelling south towards Africa. For many, the journey takes them directly through an area filled with wind turbines.
At the Barão de São João wind farm, near Lagos, that presents a particular challenge to these birds. How do you generate renewable electricity without putting migrating birds in danger?
The answer, it turns out, may be surprisingly simple. When the birds approach, the turbines stop.
A monitoring system combining radar technology with human observers recorded no deaths among soaring birds from turbine collisions during five consecutive autumn migration seasons, despite around 5,000 birds passing through the area each year.
The findings, originally published by researchers led by Ricardo Tomé, have recently attracted renewed international attention.
The wind farm sits along one of Portugal’s most important migration routes, used by more than 30 species of soaring birds, including birds of prey.
These birds often rely on rising warm air to travel long distances with relatively little effort. But their flight paths bring them dangerously close to the rotating blades of wind turbines.
Researchers found that 55% of the soaring birds crossing the area flew at altitudes associated with a high risk of collision.
To protect them, the wind farm introduced a system known as Radar Assisted Shutdown on Demand.
Observers stationed around the site watch for approaching birds, while radar helps detect movement over greater distances. When large numbers of birds are migrating, or particularly vulnerable species are spotted, the turbines can be temporarily switched off.
Rather than stopping electricity production throughout the migration season, the system allows operators to respond when the risk is greatest.
One of the most interesting findings was how little the shutdowns affected the wind farm’s operation.
During the first year, turbines were stopped for approximately 105 hours. As the monitoring team gained experience and eventually received direct access to the turbine control system, that figure fell to around 15 hours annually.
Across the study, shutdown periods represented just 0.2% to 1.2% of the wind farm’s equivalent annual operating hours.
The results suggest that careful monitoring can make a substantial difference without requiring wind farms to sacrifice large amounts of electricity generation.
The Algarve project has also attracted attention from international conservation organisations.
The Organisation for Economic Co-operation and Development highlighted the Portuguese findings in its research on renewable energy and biodiversity, noting the absence of recorded soaring bird fatalities during the initial five-year monitoring period.
Could other wind farms follow this lead?
The Algarve isn’t the only place where this approach has shown promising results.
Research involving 20 wind farms in Cádiz, southern Spain, found that selectively stopping turbines reduced deaths among soaring birds by approximately 62%, while griffon vulture fatalities fell by almost 93%.
The estimated loss of electricity production was less than 0.51%.
There are, however, important limitations to the Portuguese findings.
The five-year result applies specifically to soaring birds, the group targeted by the monitoring programme. Other bird species were still found to have collided with turbines.
Longer-term monitoring also recorded two soaring bird fatalities during the wind farm’s first decade of operation, meaning the original five-year finding should not be interpreted as a permanent absence of collisions.
Nevertheless, the research offers a practical example of how wind energy projects can be managed more carefully in environmentally sensitive locations.
For the Algarve, where migrating birds are part of the region’s natural heritage, the lesson is particularly relevant. Producing cleaner energy and protecting wildlife do not always have to be competing priorities.