How Do Thousands Of Starlings Fly Without Colliding?
You’ve probably seen it and scratched your head in amazement—a massive flock of starlings, often just before sundown, darting around in the sky in an impossibly complicated pattern, like a school of sardines trying to evade a shark.
It’s likely you’ve wondered why the birds never crash into each other, or why no stragglers ever get left behind, or how the birds seem to always maintain their place despite the shifting shape and density of the flock.
Physicist Andrea Cavagna also asked those questions, probably getting a stiff neck from staring into the dusky sky over his native Rome, watching the birds overhead. He was so intrigued by the mystery, in fact, that he spent the past three years trying to crack the code.
Now, he is happy to report, he has the key to the puzzle. STARFLAG: Starlings in Flight—a collaboration of seven European institutes that he led under the direction of the Italian National Institute for the Physics of Matter—has come up with some answers.
What’s the starling secret?
The secret is that the starlings, whether there are 100 in the flock or 10,000, use a tracking system that helps them maintain their distance from the seven other birds around them, regardless of the distance between them.
If the flock is under attack from a predator—in Rome, for example, the birds are often targeted by Peregrine Falcons—they will spread apart. At other times, such as when the flock is making a tight maneuver or directional change, they will merge much more closely together.
"They do these incredible maneuvers but they never lose birds, they are always with the flock no matter how drastically they change the shape or the intensity, they always stay together."
After one year of studying the data collected in the two previous years of the study, Cavagna said the researchers have come to the conclusion the birds base every movement on what their wing-mates are doing.
"They always interact with six or seven birds irrespective of what is the distance of these seven birds," he says.
That means that after an attack has taken place, and the flock has expanded, it can regroup very quickly because cohesion doesn’t rely strictly on the distance between the birds.
Previous research held that each bird interacted with all other birds within a certain physical distance surrounding it.
Researchers collected their data in Rome, using cameras mounted on the roofs of buildings in neighborhoods where starlings often perform their aerial acrobatics.
The flocks were photographed at the same time by multiple cameras, using a rate of 10-frames-per-second.
