First Simulation of the Flocking Behavior of Starlings

The communal aerobatic displays that huge flocks of starlings perform above their roosts of an evening are legendary.

They are also devilish in their complexity. In the last few years, complexity experts have begun to tease apart the rules that govern this kind of fantastically complicated self-organized behavior. The same sort of behavior is seen in fish, insects, and even human crowds. And while various models have been developed to simulate the behavior of many of these beings, nobody has succeeded in building a model that captures all the complexity of starling displays.

Until now. Charlotte Hemelrijk at the University of Groningen and pals have, for the first time, created a computer model that successfully reproduces their coordination during wheeling and turning, splitting and merging and the changes of flock shape and density.

The trick, of course, is not to worry too much about each bird’s individual behavior but to dream up a set of rules that govern them all. So in this case the behavior of each individual is based on its cruise speed, the position and movement direction of its neighbors, and for the first time other newly identified factors such as each bird’s attraction to the roost and the simplified physics of aerodynamic flight, which includes banking while turning.

But the key advance that has made this simulation possible is the first 3-D recordings using stereo photography of real starlings in flight, which were published only last year. That’s not for lack of trying but the great difficulty in making precise measurements of position and velocity on thousands of rapidly moving birds simultaneously.

But now that it’s done, the new data has allowed Hemelrijk and company to compare their simulation to the real thing and to fine-tune the parameters of the model to reproduce the behavior. That’s something that just hasn’t been possible until now.

The result is an impressive match that reproduces many of the amazing characteristics of the flocking aerobatics of these extraordinary fliers.

Ref: arxiv.org/abs/0908.2677: Self-Organised Complex Aerial Displays of Thousands of Starlings: A Model