Each winter, starlings gather in large flocks of up to 100,000 individuals across the UK. Most have migrated from northern Europe seeking milder temperatures and more abundant food. Their arrival is celebrated by residents outside the city of Sheffield, England where wetlands offer prime roost habitat, and the vast horizons make a perfect theater for the birds to enact a spectacular display of cohesive dance called murmuration.

At first, they trickle in: one bird here, a few birds there. Then, at dusk’s cue, a dark smudge materializes on the horizon. Thousands of starlings slowly come into focus, etching flight paths across the winter sky as they stream toward their evening roost in north-central England. Suddenly, the flock dips and twists like a horse tossing its head. It swirls into a funnel, then cartwheels to the side, shapeshifting in seemingly effortless unison.

The starlings’ murmurations sometimes give the impression that the birds are painting the sky with gigantic scribbles that resemble a Twomby artwork.

The sight of a large number of birds in murmuration endlessly teases the imagination with surreal images of what looks like a giant bird, a comet or UFO cutting across the sky.

Why do the birds perform this highly synchronized dance? Also, how do coordinate their dance moves? A 2017 study found that predation pressure is powerful driver for mumuration. That is, the birds do it because large flocks benefit from increased vigilance. Their complex flight patterns also prevent predators from honing in on a single target, increasing the odds of survival for each starling in the flock.

As for coordination, scientists’ favorite explanation is that this flocking behavior can be explained by assuming that each bird follows 3 simple rules: (a) cohesion (steer toward the average position of your neighbor), (b) alignment (steer toward the average direction of your neighbors), and (c) social distancing (avoid crowding too close to your neighbors).

That such complex behavior can be accounted for in such a breathtakingly simple way is, well, just beautiful.

Note

All photographs featured in this post are courtesy of Kathryn Cooper, a physicist-turned-photographer, who has a keen eye for understanding complex data. “I’m interested in the transient moments when chaos briefly changes to order, and thousands of individual bodies appear to move as one,” she says.