Watch
Drag to look around the flock, scroll or pinch to zoom.
How it works
- Get out of the falcon's way. Each bird predicts where the falcon will be over the next second and moves just far enough aside.
- Keep off the mountains.
- Don't bump into your neighbours.
- Fly the way your neighbours fly.
- Stay with them.
The rules are tried in that order, and each bird has only so much strength per moment, so the first rules win. "Neighbours" means the 7 nearest, however far: field studies of real starlings in Rome (Ballerini and others, 2008) found they track about seven, which keeps the flock together however dense it gets. Each bird also sees the others a moment late. A bird that is startled frightens its neighbours a little, and they theirs, so a fright runs through the flock as a wave. Set the reaction delay high and watch the wave slow down; set "catch fright" to zero and only the birds the falcon nearly hits react.
The flock engine and the mountains come from the Skyrings flight game, where the same rules move a dragon made of drones.