A wind farm in Texas is using space-age radar to shut down its giant turbine blades if migrating birds come too close.
The farm lies on a route used by millions of birds each autumn and spring.
Its operators say the radar can detect the birds from several kilometres away - and stops the turbines to let them pass.
Environmental campaigners say thousands of birds are killed each year by wind farms and they shouldn't be placed where wildlife may be threatened.
