Back in my hiking days, I noticed a black bird roosting in a nearby tree.

"I've always wondered what's the difference between a raven and a crow," I said.

"You have to count the pinion feathers on the wings," my companion explained. "If there are four, it's a crow. If there are five, it's a raven."

"Really?" I said, although I knew he didn't have a clue about which he spoke.

"Oh, yes," he replied. "It's just a matter of a pinion."