http://www.npr.org/templates/story/story.php?storyId=113435504
FLATOW: Why doesn't that happen with birds?
Prof. BARCLAY: Birds have a very different respiratory system. Their lungs essentially are stronger and can withstand that sudden drop in air pressure. And so when we were looking for bats and birds underneath wind turbines, we'd frequently come across bats that looked perfectly intact, absolutely nothing wrong with them on the outside. When we looked inside, it turns out that their lung cavities were full of blood, and the little blood vessels in the lungs had been damaged. We never find birds that look like that." />