Le 22 oct. 2021 à 16:15, Louis-Philippe Arnhem <gierz...@live.be> a écrit :
Bonne question. J'ai lu un livre concernant l'étourneau (De Spreeuw) de Hugh Gallagher (un néerlandais comme son nom ne l'indique pas), datant de 1978 dans lequel l'auteur affirmait exactement la même chose (sur l'étourneau donc). Si tu veux, je pose la question sur le forum international ?
Louis-Philippe Arnhem
Leuven, Belgium
Van: Bernard Genton <b.ge...@bluewin.ch>
Verzonden: donderdag 21 oktober 2021 20:33
Aan: Arnhem Louis-Philippe <gierz...@live.be>
Onderwerp: Van Arkel et les 70 km/hHello Louis-Philippe,
Nous cherchons à savoir de quel procédé technique précis Van Arkel s’était équipée pour affirmer que les martinets volaient à 70 km/h peu avant d’entrer dans leur cavité. Cela ne semble pas indiqué dans l’article où elle évoque ce fait.
En sais-tu plus à ce sujet en tant que gierzwaluwien distingué ?
Merci pour tes lumières, amitiés.
Bernard
Using this equipment they were able to deduce the bird's flight speed and wing-beat frequency.
Need for speed
During the study, they clocked common swifts flying at 75km/h (20.8m/s; 47mph), with one swift registering a top speed of 111.6km/h (31m/s; 69.3mph). That is the highest confirmed speed achieved by a bird in level flight, the researchers say.
Extraordinarily, the birds occasionally reached top speed while performing steep climbing flights.
Usually, common swifts fly at a relatively consistent speed of 36 to 43km/h (10 to 12m/s; 22 to 26mph), regardless of whether they are flying to a roost, migrating or flying in a wind tunnel, says Dr Henningsson.
But the birds "turboboost" their speed when they are showing off.
When common swifts come together to mate, both breeders and non-breeders fly together in a social display, which scientists call "screaming parties" based on the vocalisations the birds emit.
"They were generally known for flying very fast during this behaviour," says Dr Henningsson. "However, there were no really certain measurements of how fast these flights are. It is remarkable that a bird that otherwise appears to be 'finely tuned' to perform at a narrow range of flight speeds at the same time is able to fly more than twice as fast when it needs to."
That means the birds need to be able to radically alter their aerodynamic performance, by altering their wing profile and physiology, depending on whether they are flying normally or in a screaming party."
Cheers,
Rick