A few months back I took the train to New Haven to learn about feathers. I sought out an ornithologist at Yale named Richard Prum in his office. As soon as I walked in, he promptly picked up a manila envelope from his desk. Out of it he drew what looked like the black wooden handle of a long paint brush.

“What is that?” I asked.

“It’s a quiz,” he said. “You tell me.”

“A feather?” I guessed.

“This is a cassowary wing feather,” Prum said.

Cassowaries are flightless birds that live in Australia and New Guinea. It was hard to imagine how the stick in Prum’s hand could belong to a bird, so he led me down a hallway to the Peabody Museum’s ornithology