Many birds have the ability to make vocal cries to alert other members of their flock, but this is the first proof that flight noise can also serve as an alarm call.
Credit: Geoffrey Dabb
PARIS: Biologists have discovered that a species of pigeon has a secret way of alerting fellow birds to predators – a ‘whistle’ emitted by flapping wings when the bird takes off in alarm.
The Australian crested pigeon (Ocyphaps lophotes) is well known for the abrupt metallic-sounding whistle that it makes on takeoff. Until now, though, nobody had analysed the sound or explored whether it may have a use.
Robert Magrath and Mae Hingee of the Australian National University, in Canberra, recorded a crested pigeon as it tucked into grain on a feeding table.
Alarm call
They tossed a model of an Accipiter hawk from behind a hide to capture the sound of the bird taking off in fright. They then recorded the takeoff of a bird as it flew unprompted from a flock, unbothered by any threat.
Magrath and Hingee discreetly played back the two sets of whistles to 15 groups of pigeons to see what happened. The first whistle stirred flocks to take to the skies in panic, whereas the second caused no disturbance.
To the human ear, the two whistles may well seem simple and identical but acoustic analysis shows the sounds to be quite complex and distinct, the investigators say.
Spot the difference
The whistles each comprise two tonal elements and an atonal ‘clap’. But the ‘alarm’ version of the whistle is louder and has a more rapid tempo than the ‘non-alarm’ version – and the pigeons easily spot the difference.
Many birds have the ability to make vocal cries to alert other members of their flock, but this is the first proof that flight noise can also serve as an alarm call, the scientists believe.
The whistle is probably produced by the vibration of an unusually slender primary feather in the pigeon's wingtip, they say. This suggests that the whistle evolved not as a by-product of flight but as a warning signal to help the species survive.
The paper appears in the British journal Proceedings of the Royal Society B.
Follow Cosmos on Twitter! twitter.com/cosmosmagazine
There are large numbers of
There are large numbers of this species locally and like most people in this area we are aware that when the birds are frightened and take off the sound alerts others. What has come as a surprise is that the fact was not well known, I for one assumed that it was common knowledge. It just goes to show; we not take things for granted. What might be known to some may be a mystery to others.
Pigeon wing-whistling is not new
Here in Hawai'i we have the imported Chinese Laceneck Dove, which makes its own wing-whistle alarm should it see danger (a human) as it flys by. It's easy to observe: hide yourself where the birds frequent and observe them in normal flight. Then expose yourself as one flies by and immediately the bird will startle and speed up its wingbeats to flee. The formation of the wing-whistle (and its rising pitch) coincides perfectly with the startle/danger action of the bird. And yes, any other dove nearby will take off and away in response.