In the past couple of decades, turbine designs have changed dramatically. ...the blades' surface area is much larger, so they don't have to spin as fast to generate power. Slower-moving blades mean fewer bird collisions. Perhaps the biggest change in wind-farm safety, though, has to do with location. Wind farms cannot be built in migratory pathways, in areas with high bird populations, or in areas with special features that could possibly attract high bird populations in the future.