Crested pigeons use specialized wing feathers to produce distinct whistles during alarmed takeoff, signaling danger to the flock.
Introduction
The crested pigeon (Ocyphaps lophotes), a flocking bird, uses a unique method to alert its group of potential danger through mechanical sounds produced by its wings. These pigeons, native to Australia, have modified flight feathers that produce distinct wing whistles when they take off in alarm. This mechanism ensures rapid transfer of information about predators, enhancing the collective vigilance of the flock. Unlike many birds that use vocal alarm calls, crested pigeons rely on these mechanical sounds to signal danger, a strategy that may be employed by other flocking species as well.
The Strategy
This sound is generated by the rapid vibration of the pigeon’s highly modified eighth primary feather, which is thinner and narrower than its other feathers. When alarmed, pigeons take off more quickly and at steeper angles than at other times, which alters their wingbeat motion and thus the acoustic properties of the resulting sounds. High-speed video analysis suggests that the harmonic sounds in the whistle are produced by the vibration of the eighth and possibly adjacent primary feathers during both the upstroke and downstroke of the wingbeat. The wing movements may also cause feathers to clap together, contributing to the overall acoustic effect.
Playback experiments demonstrated that these alarmed whistles are sufficient to incite flight in other pigeons. Birds took off in alarm only after hearing the louder, faster-tempo alarm whistles, not the sounds induced by normal takeoff. Further experiments manipulating the amplitude of these whistles revealed that it is not merely the volume but the structural differences in the whistles that convey the message of alarm.
The Potential
Crested pigeons’ use of mechanical wing whistles as alarm signals opens up new possibilities for understanding how animals communicate danger. This mechanism can inspire the development of passive communication systems in robotics and artificial intelligence, where rapid and reliable transmission of information is crucial. Additionally, studying the structural modifications of the pigeon’s feathers could lead to advancements in acoustic engineering, particularly in designing materials or devices that need to produce or respond to specific sound frequencies.
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