Birds have a variety of alarm calls that warn other members of the flock about impending danger. But for some birds, the very act of taking off is enough to sound the alarm. Mae Hingee and Robert Magrath from the Australian National University have found that crested pigeons have modified wing feathers that produce distinct whistles when the birds take off quickly and steeply. That's exactly the sort of flight that they undertake when they're alarmed, and other pigeons treat the resulting whistles as cues to take to the skies themselves.
Crested pigeons are comical-looking birds that are widespread across Australia. Foraging in groups gives them some measure of protection from predators, but the birds have no alarm calls of any sort. They do, however, have whistling wings. Thanks to an eighth primary feather that is much narrower than its neighbours, the wings produce loud, almost metallic noises in flight. These are so conspicuous that birders can use them to identify the species. They have even earned the bird the nickname of "whistle-winged pigeons".
