U.S. pollution regulations meant to protect humans from dirty air are also saving birds. So concludes a new continentwide study published today in The Proceedings of the National Academy of Sciences. Study authors found that improved air quality under a federal program to reduce ozone pollution may have averted the loss of 1.5 billion birds during the past 40 years. That's nearly 20 percent of birdlife in the United States today. The study was conducted by scientists at Cornell University and the University of Oregon.