A flock of birds seems to have a mind of its own, turning and undulating as a unit. Yet there is no central leader. The flock coordination emerges from the individual birds following very simple rules. Here is a model of two types of birds flocking (click here). Red birds only flock with red, blue with blue. The simulated birds pay attention only local neighbors, yet global patterns emerge.
Here’s essentially same model but with Halloween bats (and Bach’s Toccata and Fugue).