The One Voice in Ten Thousand

In the Antarctic winter, an emperor penguin colony can number over ten thousand birds, all huddled together on the ice in a single dark mass of feathers. When a parent returns from weeks of fishing at sea, it faces what seems an impossible task — finding its one chick among thousands of nearly identical birds. Yet the parent opens its beak and calls out a unique two-tone frequency, a vocal signature as distinct as a fingerprint.…