But he offers two explanatory hypotheses.Īccording to the first hypothesis, it could be that female hummingbirds prefer to mate with the best flyers because of their relatively high fitness and that females use the volume of a suitor's tail feathers as a proxy for his fitness. Females choose a mate from among available males.Ĭlark is unsure why male hummingbirds have evolved an ability to generate sounds with their tail feathers during courtship. In addition to diving during courtship rituals, a male hummingbird may also brandish showy ornaments and produce sounds from other feathers besides his tail feathers. Also, the faster a male hummingbird dives, the louder his fluttering sounds become. When diving during their courtship dances, male hummingbirds exceed their usual flight speeds - with birds of at least some hummingbird species reaching their possible maximum speeds during dives. "The sounds that hummingbird feathers can make are more varied than I expected," said Clark. Other factors, such as the size, shape, mass and stiffness of the hummingbird's feathers, also help determine the tone of each species' particular sound. What's more, neighboring feathers that flutter at the same frequency produce a different tonal sound than neighboring tail feathers that flutter at different frequencies. When interacting in this way, a hummingbird's neighboring fluttering tail feathers produce a sound that is louder - usually about 12 decibels louder - than would the two tail feathers fluttering independently of one another. For example, the fluttering of one of a hummingbird's tail feathers may cause a neighboring feather to flutter, similar to the way that the vibrations of one tuning fork may cause another nearby tuning fork to similarly vibrate. This spreading exposes the tail features to air, which causes them to flutter and generate sound.Ĭlark's research, which he began as a graduate student at the University of California at Berkeley, shows that the males of each hummingbird species have their own signature sound - largely determined by whether and how the fluttering frequencies of its different tail feathers interact with one another and blend together. Typically, during such a display, a male hummingbird will climb into the air five to 40 meters, and then quickly dive-bomb down past a perched female when the courting male bird reaches the lowest point of his dive, he rapidly spreads and then closes his tail feathers. Male hummingbirds only produce fluttering sounds during their elaborate courtship rituals. View a video of hummingbird feathers fluttering in a wind tunnel. 9, 2011 issue of Science by Christopher Clark of Yale University reveals that air flowing past the tail feathers of a male hummingbird makes his tail feathers flutter and thereby generate fluttering sounds. Now, for the first time, the cause of these sounds has been identified: a paper published in the Sep. "But then we noticed that the sounds were actually coming from these black hummingbirds.Though famous for their mid-air hovering during hunting, tiny hummingbirds have another trait that is literally telltale: males of some hummingbird species generate loud sounds with their tail feathers while courting females. "We heard prominent high-pitch sounds that sounded perhaps like a cricket or a tree frog," Mello said in a statement. Reports of the jacobin making high-pitched sounds have been published before, but never investigated by Dr Claudio Mello of Oregon Health and Science University, who came across the phenomenon by chance when doing field work in the jacobin's habitat. The black jacobin inhabits South America's Atlantic mountain forests. It's unclear at this point whether even other members of the black jacobin ( Florisuga fusca) species can hear the sounds they produce, and if not, what purpose they might serve. Nevertheless, ornithologists didn't expect to come across a species that makes sounds so high pitched they are out of the known hearing range for birds. They're also known for the diversity of the sounds they make. Hummingbirds are the extreme athletes of the avian world, living fast thanks to having the highest metabiolism of any bird or mammal.
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