Bird flock A flock of birds hundreds strong
wheeling in perfect synchrony overhead is one of nature's great sights.
If a single bird fell out of line, utter confusion could ensue, yet none does.
Harmony reigns, spawning a behavior (flocking, with its swift motion and sudden
course changes) that is not predictable from knowing all there is to know about
any single bird. Flocking "emerges" from simple rules instinctively
followed by each bird: keep a precise distance away from and stay aligned with
your nearest neighbors, and avoid predators. The "wave" in a
stadium operates along similar lines (minus the predator part).