Amazing footage of starlings flocking

What amazes me is how all the birds turn at once. What signals them? A sound, the wind currents, something else? They all turn at the same time in the same direction, not crashing into one another. It's always something I've wondered whenever seeing a flock of birds flying together. Pretty amazing really.

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Emergence is said to arise from the cooperation of many simple processes, i.e. high-level behaviour resulting from low-level interaction of simpler building blocks.

One example of emergent behaviour that has been studied over recent years is that of 'flocking'. In a 'flock of birds', the flock is a dynamic entity consisting of hundreds (or thousands) of individuals.

The flock constantly changes shape and direction but maintains overall cohesion. Using cellular automata and treating each bird in the flock as an autonomous agent, with simple local rules controlling agent behaviour relative to closest neighbouring birds, a system can be constructed where the overall behaviour of the collective agents reflects the behaviour of the real flock.