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Why do birds sing? Why are their songs so melodious? Meeting with the naturalist Stanislas Wroza, specialist in eco-acoustics. He listens and records the songs of birds.
We stopped in a clearing in the forest of Fausses-Reposes, in Ville d’Avray, on the heights overlooking Paris to the west. The sun was playing with the clouds. The wind blew through the branches of the trees. And the birds were singing. So he took out a strange object, a satellite dish equipped with a microphone nestled in his heart, and connected to a helmet that he put on his ears. A technical device supplemented by a recording device. The sound “show” was about to begin.
Stanislas Wroza listens to the birds. Record their songs and cries. Lists them and, like hundreds of volunteers, participates in enriching the INPN, the National Inventory of Natural Heritage. “This is what allowed us, the first, to show that there was a 25% decline in bird populations in France since 1989.underlines the man who heads the Evaluation and monitoring team within PatriNat, a living expertise unit set up by the French Office for Biodiversity, the National Museum of Natural History and the National Research Center scientific. Less 25% of birds in 30 years, and even less 40% in agricultural areas! The reason we are interested in birdsong is that they are often hidden in bushes, in foliage, and it is really difficult to see them. » Eco-acoustics, the act of listening to and recording the sounds of nature, is the ideal way to survey bird populations.
Eco-acoustics to listen to nature
Armed with his satellite dish, headphones on, Stanislas Wroza performs “a 360”for 360 degrees, a complete rotation on itself to capture the birds around us. “I hear a robin… I hear a song thrush way over there (the parable makes it possible to perfectly isolate sounds located up to 200 meters, and even beyond), a chiffchaff, which is just in front of us… A blackcap and its very creative song. Then… I hear the great spotted woodpecker, a second robin, and if I finish my 360, I come across another blackcap, a great tit and a blue tit. So that makes about ten species in one turn of the parabola. This makes it possible to go fairly quickly in detection! »
Humans talk, and birds sing. Some are more harmonious than others, but all want to communicate. “Birds sing first to mark their territory”explains Stanislas Wroza, author of several books on the subject, including Birds through sound: recording, identifying, understanding (Delachaux and Niestlé editions). When we arrived in the forest, a buzzard hovered above the trees in peaceful silence. A little later, two other buzzards arrived, and the concert began, as if to say “this is my home. »
When the sun shines, the birds sing
“ Birds also sing to find a mate », continues the creator of the site soundbirding.org. The birds sing, but also cry. “It’s an alarm call, in a stressful situation, in the presence of a predator or when approaching the nest. And then there are repertoires like flight calls. If there are birds below that belong to my species, they will respond to me. »
A large cloud hid the sun above the forest of Fausses-Reposes, and when it returned, the birds began to sing again. “There is a ray of sunshine, the wind has stopped, and all of a sudden it starts up again. Birds are sensitive to the weather. There is enormous activity in the morning, and later in the day, whenever there is a ray of sunshine, it usually starts singing again. »
The very creative song of the blackcap
Is singing in birds innate or acquired? A bit of both. “Experiments have shown that when a bird is reared by a species other than its own, it will tend to take on the song of the other species. This shows that there is still a good deal of learning. In Australia, a species of bird is so threatened with extinction that young individuals can no longer even learn their own song! »
In the class of birds, not everyone is equal when it comes to song. “There are species that have very simple songs, which resemble those of grasshoppers. Basically it’s a note that we repeat a hundred times in a row tirelessly. And then there are some species that are very, very creative with extremely complex songs. The black-capped warbler, for example, can use 70 to 80 notes easily in its song. And in addition include imitations of the species in its entourage. It’s a way to show that you have a form of creativity and intelligence, and therefore that you are a good breeder. »
Birds sing better than humans
The extremely complex and melodious song of the blackcap, no human voice can reproduce it. “The vocal organs of birds are different from those of human beings.explains Stanislas Wroza. We have vocal cords that allow us to make only one sound at a time. In birds, it does not happen the same way. They have a syrinx, which is made up of two different channels. What makes that they are able to make two notes at the same time. » When we left the forest of Fausses-Reposes, the sun had won its part against the clouds, and hundreds of notes accompanied our departure. The birds would sing until evening.
“Why do starlings fly in clouds? »
Swirls of starlings at sunset. a flamboyant ballet that brings together thousands and thousands and thousands of individuals – we call it murmurations. The starling is one of the most gregarious birds, and these gatherings in the sky are the signal that it is time to go to sleep, all together. In nature, unity is strength, and these cloud flights are also a way to protect themselves from predators, raptors. But beware of bird strikes. The most serious plane accident caused by birds sucked in by the reactors took place in the United States in 1960. Sixty-two deaths caused by starlings.