FW: Van Arkel et les 70 km/h

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Louis-Philippe Arnhem

Nov 4, 2021, 7:58:27 AM11/4/21
to Swallows-Martins-Swifts-Worldwide, Bernard Genton, Gierzwaluwen

Our friend Bernard Genton from Switzerland is trying to find out what precise technical process Van Arkel used to say that swifts were flying at 70 km / h shortly before entering their cavity. This does not seem to be indicated in the Dutch article where he discusses this fact.

Any thoughts ?

Louis-Philippe Arnhem
Leuven, Belgium

Van: Bernard Genton <b.ge...@bluewin.ch>
Verzonden: zondag 24 oktober 2021 16:15
Aan: Louis-Philippe Arnhem <gierz...@live.be>
Onderwerp: Re: Van Arkel et les 70 km/h
Oui, bien volontiers, merci !

Voici un extrait de sa publication.

A bientôt.


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/h
Hello 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.


1997 Arkel - copie.pdf

Rick Wortelboer

Dec 12, 2021, 5:24:09 AM12/12/21
to Gierzwaluwen
Hi Louis-Philippe and Bernard,
Any clues about the alleged flying speed? I think it might come from hearsay.
An important factor is of course the trajectory of the flight to the entrance and the point in that trajectory to make the speed measurement. The obviously do not enter a nestbox at 70 km/h.
At my place the nestboxes have an entrance directed 30-45 degrees downward. Therefor they do approach the nestbox from below. In the last metres they fly upward thereby losing part of their speed and having to brake less in the last metre.
Perhaps a very fast film camera can record their flight and speed may be deduced from the recordings?
Success with your search.

Rick Wortelboer

Dec 12, 2021, 5:32:25 AM12/12/21
to Gierzwaluwen
With a bit of googling, I found an article at BBC Earth News (http://news.bbc.co.uk/earth/hi/earth_news/newsid_8539000/8539383.stm)

Confirmation of the new record came as Dr Henningsson and Lund University colleagues Dr Christoffer Johansson and Professor Anders Hedenstrom filmed common swifts using two high speed cameras.

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.


Also surprising is the circumstances in which the swifts fly so fast.

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."



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