Why starlings do this
On winter evenings, European starlings gather above their roosts and fly in dense, shape-shifting clouds called murmurations. Everything below is true of the real birds; everything above is a simulation that borrows their rules.
Seven neighbours
Starlings don’t track the whole flock. Research from the STARFLAG project (Ballerini et al., 2008) found each bird coordinates with roughly its six or seven nearest neighbours — regardless of how far away they are. That local rule is what lets a hundred thousand birds turn as one.
Safety in the swirl
Murmurations usually form at dusk, before the birds drop into a communal roost. The constantly shifting cloud is thought to confuse aerial predators such as peregrine falcons, which struggle to single out one bird from thousands of moving targets.
Hundreds of thousands
Large winter roosts in Europe can draw flocks in the hundreds of thousands. Famous murmuration sites — Brighton’s piers, the Somerset Levels, Rome’s city centre — pull in birdwatchers every winter for a display that lasts maybe forty-five minutes before the light goes.
Three rules are enough
In 1987, computer graphics researcher Craig Reynolds showed that flock-like motion emerges from just three steering rules per bird: separation (don’t crowd), alignment (match your neighbours’ heading), and cohesion (drift toward the local centre). His “boids” model is exactly what powers the sky above.
What you’re watching: a boids simulation — six hundred digital birds following Reynolds’ three rules, with a fourth gentle urge that periodically pulls them into letterforms. Real starlings, to be clear, do not spell.