No, no, not mankind ... starlings !!
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| Jacques Callot |
Amazing Starling Flocks Are Flying Avalanches
"In particle physics, synchronized orientation is found in systems with “low noise,” in which signals are transmitted without degrading. But low noise isn’t enough to produce synchronized speeds, which are found in critical systems. The researchers give the example of ferromagnetism, where particles in a magnet exhibit perfect interconnection at a precise, “critical” temperature.
“More analysis is necessary to prove this definitively, but our results suggest” that starling flocks are a critical system, said study co-author Irene Giardina, also a University of Rome physicist.
According to the researchers, the “most surprising and exotic feature” of the flocks was their near-instantaneous signal-processing speed. “How starlings achieve such a strong correlation remains a mystery to us,” they wrote."
Scale-free correlations in starling flocks
From bird flocks to fish schools, animal groups often seem to react to environmental perturbations as if of one mind. Most studies in collective animal behavior have aimed to understand how a globally ordered state may emerge from simple behavioral rules. Less effort has been devoted to understanding the origin of collective response, namely the way the group as a whole reacts to its environment. Yet, in the presence of strong predatory pressure on the group, collective response may yield a significant adaptive advantage. Here we suggest that collective response in animal groups may be achieved through scale-free behavioral correlations. By reconstructing the 3D position and velocity of individual birds in large flocks of starlings, we measured to what extent the velocity fluctuations of different birds are correlated to each other. We found that the range of such spatial correlation does not have a constant value, but it scales with the linear size of the flock. This result indicates that
behavioral correlations are scale free:
Understanding behavioral patterns: Why bird flocks move in unison
Using a simple self-propelled particle (SPP) system, which sees the birds represented by particles with such parameters as position and velocity, the researchers from Budapest, Hungary, find that the collective switching from the flying to the landing state overrides the individual landing intentions of each bird.
In the absence of a decision making leader, the collective shift to land is heavily influenced by perturbations the individual birds are subject to, such as the birds' flying position within the flock. This can be compared to an avalanche of piled up sand, which would occur even for perfectly symmetric and cautiously placed grains, but in reality happens much sooner because of increasing, non-linear fluctuations.
"The behavior of the flock of starlings is different to the behavior of a group following a leader. Such a group would move in the same direction and would appear strongly ordered, but there would be no passing of information between individuals, and so, behavioral fluctuations are independent, with changes in direction of an animal other than the leader having little effect on other members of the group. The starlings’ behavior is an example of self-organization, and the collective response to events such as attack by predators gives them a distinct advantage."
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| Collège de Navarre |
