Volcán Antisana (Ecuador) (AFP)
Its song has long been confused with the murmur of the wind in the Ecuadorian moor, but scientists today marvel at having discovered the countertenor bird: a hummingbird with a unique song, the highest of all.
Commonly called "the little Ecuadorian star", this hummingbird barely 14 centimeters tall is capable of making high-pitched sounds.
Oreotrochilus chimborazo sings at a fundamental frequency of 13.4 kilohertz (kHz), which can go up to 16 kHz, according to a study published in July in the journal Science Advances, when the vast majority of birds emit sounds ranging from 2 to 8 kHz.
"The fundamental frequency is important because it indicates the frequency at which the syrinx, the equivalent of our larynx, which produces sound, vibrates," Fernanda Duque, Ecuadorian neuroscientist from the University of Georgia, in the United States, told AFP. united, author of the article.
Still amazed by her discovery after five years of work, the 32-year-old scientist notes that some hummingbirds emit vocalizations that reach 8 kHz, "but it is rare to hear songs above 10 kHz, which is why these vocalizations are important, ”she explains.
In addition, "the little Ecuadorian star" is the only hummingbird that can live at 5,200 meters above sea level, defying the extreme cold of the Ecuadorian paramos, these humid high altitude moors of the equatorial regions, a vital ecosystem which acts like a sponge retaining the water.
The country has some 130 species of hummingbirds, or 40% of the 300 recorded on the American continent, the only one where they live.
- "A sssss" -
The males of the Oreotrochilus chimborazo species utter a song so loud that it can drown out the sound of the wind hitting the moor and the chuquiragua, these shrub plants that are their favorite food.
"I heard that sound, but it didn't even occur to me that it might be a bird's song. To me, it sounded like the whisper of the wind in the meadow, like a 'sssss' ", remembers the husband of Fernanda Duque, the Ecuadorian scientist Carlos Rodriguez, 33, who studies the evolution of birdsong at the University of Texas, in the United States.
He even thought that sound was the buzz of an insect.
"But I found that every time I heard that sound I saw the hummingbird," he explained.
And "among the sounds we are used to hearing, whispers are those with higher frequencies, higher than whistles," he points out.
And with age, he recalls, hearing abilities decrease and are no longer able to pick up the hummingbird's countertenor song.
Oreotrochilus chimborazo lives in the Chakana Nature Reserve, on the slopes of the Ecuadorian volcano Antisana (50 km south-east of Quito), where the study was carried out.
It is in this habitat that Efraín Cepeda, member of the Jocotoco Nature Protection Foundation, also observed it.
When the hummingbird begins to sing, perched on the chuquiragua plant, its neck widens and the feathers of its head move as if to form a wave that changes color by iridescence, he explains.
This hummingbird has a crown that goes from purple to blue, depending on the light.
These colors and the frequency of his song are the mode of communication he uses "in specific social contexts which are the defense of a territory and seduction", explains Fernanda Duque.
The researcher also identified that the males and females of Oreotrochilus chimborazo live on different territories and that only the males interpret this high-pitched song, more complex than the other vocalizations that the species can perform.
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