Starlings Coordinate Movements Within a Flock

flock of black birds flying across green grass and blue sky

Biological Strategy

European starling

Sam Stier

Image: Artur Rydzewski / Flickr / CC BY NC - Creative Commons Attribution + Noncommercial

Coordinate by Self-Organization

To create and maintain a healthy community of individuals and ecosystems requires that living systems coordinate their activities. Coordination doesn’t necessarily mean that there’s a leader orchestrating what happens. In nature, coordination is usually achieved through self-organization. In a flock of geese flying in a V-formation, for example, there’s no lead goose controlling where all of the others fly. The flock uses this formation because each goose gains energy from air vortices created by the goose in front of it. The lead goose doesn’t gain that benefit, so when it tires, it moves back and another goose takes the front position.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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Starlings stay together within a flock by paying attention to the movements of the seven other birds closest to it

When you are driving in a large group of cars to some destination, you only need to pay attention to the car driving directly ahead of you to stay in the group. But what if you were trying to stay together with a whole group of cars, flying through the air together? This is what flocks of starlings must do. Starlings fly together in large groups, often every evening, circling through the same portion of sky almost as though for the fun of it. In fact, researchers are not even sure why starlings do these coordinated dances. Starlings are able to stay within inches of other starlings, in groups of hundreds or thousands of individuals, turning at high speeds, without ever colliding. How do they do this?

A group of birds with circles and arrows indicating how they track each others' movements

Starlings are able to manage these high-performance acrobatics by paying close attention to the speed and direction of the other starlings around them. However, starlings don’t pay attention to all the other birds in the flock at once. A starling just needs to pay attention to the movements of the seven other starlings closest to it. Any fewer, and there’s not enough reliable information for a starling to maintain flying with precision within the flock. Any more, and there’s too much information to process quickly and make real-time decisions. It turns out that seven neighbors is the ideal number, regardless of how large or dense the flock is.

The way starlings coordinate their behavior with an optimal amount of information has many lessons for people. We have to make decisions often with too much information at our fingertips. How much information is enough? Starlings remind us that there is a balance between having enough good information to make decisions, and learning to filter out the rest.

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References

“Our analysis shows that the size (seven) of each starling’s neighborhood optimally trades off gains from robustness with costs associated with sensing and attention…” (Young et al. 2013:4).

“More generally, our work demonstrates the significant role of who is interacting with whom in the ability of a network to efficiently manage uncertainty when seeking to maintain consensus. This suggests possibilities for understanding and evaluating uncertainty management in other social and technological networks.” (Young et al. 2013:6)

“Previous work has shown that starlings pay attention to their seven closest neighbors, but until now it was not understood why this number is seven. Our paper explains the mystery: when uncertainty in sensing is present, interacting with six or seven neighbors optimizes the balance between group cohesiveness and individual effort.” (Young et al. 2013:2)

Journal article