Lhe hero of our daily column is well known to regular readers of this newspaper. No earlier than Saturday May 28, M The magazine of the World even devoted its cover and a remarkable investigation to the jackdaw and the controversies born of its proliferation. To this famous main course, we propose today to add a little dessert with a scientifico-political coloring.
The team led by Alex Thornton, at the University of Exeter (Great Britain), devotes its research to the challenges posed by the social life of animals. This time, the inspiration came from the swarms of jackdaws springing up every morning from the trees in the neighborhood. “We wondered how they decided to leave together”, he says. The answer, given on May 23 in the review Current Biology, He sums it up in a few words: “By vocal consensus.”
The quest for consensus in animals is not a new object of study. Over the years, scientists have already noted behaviors “democratic” in several species, from bison to macaques, from capuchins to buffaloes, from deer to bees, from meerkats to wild dogs. Through sound or gesture, individuals express their readiness to leave a place of rest, sometimes even indicate the direction they wish to take. And in its great wisdom, by a typically collective intelligence, a decision is made, as long as the quorum is reached.
The Cornish researchers came to the same conclusion. Hours of audio and video recordings of six groups of jackdaws, numbering 160 to 1,500 individuals, revealed an almost unchanging pattern. The first cries rise well before sunrise. They call others. The concert increases in intensity, over several tens of minutes. Then suddenly, in a few seconds, most of the birds fly away. This “explosion”, the scientists were able to observe that it intervened from a certain sound level or following a sudden rise in intensity. Without such a quorum, the birds wait and end up scattering in pairs or small groups. “Observing such a difference, depending on whether the birds reach a consensus or not, was for me the most impressive result”underlines Alex Dibnah, the first author of the article.
rallying cry
But do the sound parameters actually cause the start? In other words, is there causality or simple correlation? To determine this, the scientists added to the ambient cacophony additional recordings of corvids in a third of the cases, wind noise in a second third and nothing at all in the third. Conclusive result: by their enticed cries, the birds of the first group took off six and a half minutes before those of the other two samples.
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