This audio story is brought to you by BirdNote, a partner of The 蜜柚APP. BirdNote episodes air daily on public radio stations nationwide. 8738 Transcript: This is BirdNote. Webbed feet are ideal for birds that swim, on the water’s surface or under. In fact, they’re such a nifty adaptation that they evolved, independently, in several bird groups. Ducks and geese have them, as do gulls, cormorants, loons, pelicans, penguins, puffins and boobies. Experiments suggest that a triangular webbed foot is beautifully designed to propel a bird, or other creature, through the water. The toes and webs spread out as the bird pushes its foot backward. Then as the bird pulls its foot forward, the toes fold together, to minimize resistance. And many birds have mastered a stroke that any human swimmer might envy. A bird may lift its foot away from its body on the forward stroke, actually giving itself a little extra lift and speed. Four hundred...