Many penguin pairs mate for life. That means that each nesting season, they return to the same rookery and must find their partners among thousands of birds wearing the exact same outfit. How do they do it? When first pairing up, they sing a duet and learn to distinguish their mate’s voice from all others. Imagine Sonny Bono landing on an island inhabited by thousands of Cher impersonators. He wanders around singing “I Got You Babe” until someone joins in on pitch and right on cue. That’s pretty much how it works.