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.
Now a study published in July in the Proceedings of the National Academy of Sciences explains their behavior in an elegant model.
The mystery behind the movements of flocking starlings could be explained by the areas of light and dark created as they fly, new research suggests. The research found that flocking starlings aim to maintain an optimum density at which they can gather data on their surroundings. This occurs when they can see light through the flock at many angles, a state known as marginal opacity. The subsequent pattern of light and dark, formed as the birds attempt to achieve the necessary density, is what provides vital information to individual birds within the flock.
Revealed: The mystery behind starling flocks, Science Daily, 18 July 2014
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!
Click here to read more in Science Daily.
(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 Science Daily)
I know these birds are considered invasive here, but it’s breath-taking to see this phenomenon each autumn. Along the parkway west, near Settlers Cabin park, is a good place to catch a glimpse.
One year, I pointed out a wheeling flock to a coworker as we sat outside on break. She was dumbfounded by the spectacle, and actually thought they were fallen leaves, caught up in a gust of wind!
This reminds me of an exciting experience I had in Florence, Italy. It was something I had never seen before; a “murmuration” of starlings that didn’t seem to be related to predators, but maybe it was. It occurred at sunset late last December in a courtyard of Santa Maria Novello outside the cloisters/Spanish Chapel.
There were three small bare trees in this courtyard. Thousands of birds would perch on the branches for a few minutes, then (as one) flew up into the air and formed an elongated, fluctuating vortex not unlike the one in the video. They flew around for a while, then settled again on the branches. After a few minutes they did the same thing. We watched them do this repeatedly for about 20 minutes, when we had to leave. It was one of the oddest experiences of an intensely memorable trip.
The only other thing I’ve seen that was remotely like it was a swarm of millions of ladybugs at Sandia Crest near Albuquerque. They were everywhere, flying into peoples’ eyes and noses and ears. You wouldn’t dare open your mouth. We fled to our car after a couple of minutes.