Pigeons turned out to be able to communicate with the noise of their wings: specialized feathers create acoustic vibrations, signaling danger right at the moment of a hasty takeoff.
The crested pigeons Ocyphaps lophotes inhabiting the arid regions of Australia are quite close relatives of our gray-headed ones and are able to understand each other “without any words”, reacting to the flapping of the wings of neighbors who take off in danger. This is reported in an article by Trevor Murray and colleagues at the Australian National University published in Current Biology.
It is worth saying that "non-verbal" communication is quite common in the animal kingdom. All of them in motion produce sounds that can be useful to those who know how to understand them. Some birds, such as the South American Manakin King, use the sound of their wings during mating rituals. However, no one has yet dared to call this a full-fledged communication like bird songs. The work of Murray and his co-authors studying crested pigeons could change that.
These birds have 10 primary flight feathers on each wing. Scientists have found that the eighth - and the third feather, if you count from the tip of the wing - is different from the rest. It is longer and has an unusual shape, and it was suggested as early as 2009 that it is the main contributor to the high- and low-frequency sounds characteristic of the flapping wings of a fast-flying bird.
Australian researchers used high-speed video and audio recording experimenting with pigeons, including those lacking certain wing feathers. This made it possible to show that it is the eighth flight feather that creates the sound when, when the wing moves downward, air breaks off its tip and makes it vibrate at a high frequency. In this case, the feather closer to the base of the wing can amplify this tone, and the feather closer to the end of the wing can create another, lower sound.
With the bird taking off quickly, these tones alternate with increasing frequency. Scientists have demonstrated that such sounds are indeed perceived by other pigeons as a signal of danger, including when playing audio recordings without demonstrating the bird itself producing these popping. The presence of high-frequency sounds from the eighth feather turned out to be key: upon hearing them, the birds immediately took off.