Convection And Diffusion
As Tu and Toner note, this process is highly analogous to a method of transferring heat known as convection. Convection occurs whenever you heat a pot of soup. The stove first heats the soup on the bottom. Then, the liquid on the bottom rises to transfer its heat directly to the colder stuff on top. Convection is the most efficient way to transfer heat on large scales. In the bird flocking model, the carrier of information (the bird) moves through the flock to distribute its information. In the flocking model, convection is the most efficient way for spreading information and diluting the effects of errors.
In ferromagnets, by contrast, information and errors spread only by a slower, less efficient process known as diffusion: each atom stays fixed and information travels from neighbor to neighbor until it is transmitted through the entire material. But like an ink drop spreading through a cup of water, diffusion is slow and the errors are more burdensome as they are shared by fewer birds. In the bird flocking model, it is truly the convection process that makes the difference.
The theory of bird flock dynamics is still in its infancy. The theory does not
yet factor in many external cues that birds may use, such as seasonal
temperature and even the Earth's magnetic field (some birds have magnetic
material in the brain which help them to navigate using the Earth's magnetic
field). But for non-migrating birds travelling over short distances, and for
many other groups of
Contact: Ben Stein
American Institute of Physics