Flock Warning

When crested pigeons spot a predator, they give a little whistle. But the sound doesn't come from their beaks. And [according:comparable] 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:assurance] in part because it has so many eyes watching for danger. But it's not clear how an [individual:independent] 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:feedback] could produce a lot of false alarms. So how can birds tell when their [flockmates:entrees] are seriously headed for the hills?[scientists:Researchers] 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 made by wings flapped in terror includes a distinctive sort of whistle.That noise alone will scatter a flock of feeding [pigeons:birds] 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."