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Science  19 Dec 2008:
Vol. 322, Issue 5909, pp. 1763
DOI: 10.1126/science.322.5909.1763d

Whereas jokers wonder about chickens crossing the road, scientists ponder why starling flocks land. The answer is, apparently, because everyone in the flock wants to.

The speed, agility, and cohesion of starling flocks are both beautiful and puzzling. István Daruka of Eötvös University in Budapest designed a digital flock of 200 starlings to model the rapid shift from foraging flight to landing. The model, based on field observations, describes the starlings as independently moving points in space, each with a ranking of “landing intent” that can vary from zero (the bird doesn't want to land) to one (the bird definitely wants to land).

The results, published this month in the Proceedings of the Royal Society B, show that a single starling decides to land when the average landing intent of nearby birds—presumably signaled by body language—crosses a critical threshold. Mathematician Andrew Wood of the University of York in the U.K. says most models of complex biological systems do not consistently account for individual reactions to objects, in this case neighboring birds. “It is very welcome to see this work addressing this directly,” he says.

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