Fact: Windmills can potentially have impacts on birds through collisions and habitat disruption. However, the impact is very small, and dramatically less than that of urban sprawl, buildings, house cats or climate change. For example, one study notes that for every 10,000 birds killed by human activities including fatalities by collisions with man made structures, less than one death is caused by a wind turbine. For every 1 bird death caused by a wind turbine, 1,000 to 2,000 bird deaths are caused by cats. Even the National Audubon Society strongly supports wind power as a clean alternative energy source that reduces the threat of global warming.