Birdsong helps clean the air and cultivate life.

 "But this symphony isn’t just for the birds. Chirping actually can stimulate trees to open their stomata, the tiny pores on the underside of leaves that let out oxygen and take in carbon dioxide, moisture, and minerals. Birdsong helps clean the air and cultivate life."


http://places.designobserver.com/feature/the-shape-of-green-sustainability-and-aesthetics/34518/