This audio story is brought to you by BirdNote, a partner of the 吃瓜黑料. BirdNote episodes air daily on public radio stations nationwide. 7536 Transcript: This is BirdNote. Many owls roost in trees, often spending consecutive days around the same concealed perch and venturing out at night to hunt. A roosting owl commonly leaves visual clues to its whereabouts: a scattering of furry, oval objects on the earth below its perch. They are owl pellets. Because owls often swallow mice, voles, small birds, and other prey whole, their digestive system has to deal with bones, fur, and feathers. The owl’s gizzard performs a kind of sorting operation: Soft tissues pass through to be digested, while indigestible sharp and hazardous bits like bones, teeth, and fur are formed into an oval mass. They pass back up the digestive system and are regurgitated as a pellet some hours later, often while the owl is at roost. Quite a few other kinds of birds do this, from...