Nov 04 2014
Watch this video of a starling flock evading a peregrine falcon in Torino, Italy and you’ll see some truly amazing coordinated flying.
How do starlings wheel and turn in such tight balls? How do they compress and expand without hitting each other? The mystery has puzzled humans since the first time we saw it and recent explanations that each bird keyed only on his nearest wing-neighbors did not seem to answer the problem.
Using agent based modeling of self-propelled particles researchers from the University of Warwick’s Department of Physics created a simulation that behaves just like a starling flock attacked by a hawk.
Their video below plays the simulation twice. Isn’t it uncanny how much this matches what the flock is doing above?
Changing patterns of light and dark within the flock are the key to each bird’s movement. They all want to be near each other but they need to see what they’re doing. The team writes, “We show that large flocks self-organize to the maximum density at which a typical individual still can see out of the flock in many directions.”
Lead researcher Daniel Pearce explains the model’s rules: “Each bird is represented by a particle which each have an identical set of rules to follow (and likelihood of making a mistake). In this case the rules are (a) follow your nearest neighbour and (b) move towards the areas of the projection containing the most information. When lots of these particles are introduced, the result is a collective motion much like that of a real flock of birds.”
What is “information” in this context? The technical answer is “the birds fly toward the resolved vector sum of all the domain boundaries.” Hmmmm!
(peregrine-starling video by “greenkert” on YouTube. Simulation video by Daniel Pearce on YouTube. Information from University of Warwick, Revealed: The mystery behind starling flocks” in ScienceDaily)