60秒科学:Whistle While You Wing（在线收听）

Whistle While You Wing
A study in the Proceedings of the Royal Society B finds that pigeon wing-flapping produces distinct whistles, which can warn flock-mates, when merely taking off or when actively escaping predators. Karen Hopkin reports

When crested pigeons spot a predator, they give a little whistle. But the sound doesn’t come from their beaks. And according to a study published by The Royal Society, that whistle warns the rest of the flock to flee.

There’s safety in numbers, and a flock offers protection in part because it has so many eyes watching for danger. But it’s not clear how an individual sounds the alarm when it spots a predator. Maybe anytime one or two birds fly off, they all do. Just in case. Of course that kind of knee-jerk reaction could produce a lot of false alarms. So how can birds tell when their flockmates are seriously headed for the hills?

Scientists recorded the sounds made by the wings of crested pigeons during a routine liftoff (wing sound 1). And the noise their wings make during an emergency takeoff (wing sound 2). And they found that the sound make by wings flapped in terror includes a distinctive sort of whistle.

That noise alone will scatter a flock of feeding pigeons just as quick as the shadow of a passing hawk. And gives a whole new meaning to the expression, “on a wing and a prayer.”

—Karen Hopkin