"Hoot!" is what the barn owl says when it feels like vocalizing. But when it flies, it's deathly silent. That's a feat of evolution that isn't found with most other birds. So how does the barn owl manage to keep so quiet as it glides through the night, ready to feast upon some hapless mouse or other small rodent? A new episode of BBC Earth examined this phenomena in a studio, using sensitive microphones to record the sound of a barn owl flying compared to a pigeon. Watch the following clip for yourself and find out how owls stay so quiet in motion.