Flocking Starlings

I was driving along  I-75 north of Bay City, Michigan, in an area of open fields in the flatlands of the Saginaw Valley, when I saw what I thought was a distant swirl of black smoke. I looked more closely and realized that it was a single flock of thousands or maybe tens of thousands of starlings in flight. They were a mile or more away, too far for individual birds to be visible, which gave the flock the appearance of a large dark cloud sailing over the field.

But what caught my attention was the swirling and graceful movements of this mass of birds. It was so striking and unusual that I pulled over onto the shoulder of the highway, breaking the law for a better look. The flock was passing in sweeping whorls and slow curves that made me think of smoke swirling in the vortex of a passing car. It was  mesmerizing. Here in mostly wooded Michigan we don’t get many open views, and can usually watch flocking behavior for only a few moments at a time.

As I watched I noticed a larger speck isolated at the center of a whorl within the flock. It took a moment to realize it was a hawk diving through the birds like a barracuda through a school of minnows. The flock morphed into a funnel, with the hawk plummeting through the open neck. The shape was like an Einsteinian diagram of curved space, or an artist’s  rendition of galaxies being sucked into a black hole. There was something about it that reminded me also of iron filings in a magnetic blossom. The hawk turned for another assault, and the flock switched and turned, then spiraled into shapes no geometry has  yet named.

What makes congregations of this sort stay together? How can birds in a flock or minnows in a school make such apparently instantaneous switches, dives, swoops, and banking turns without crashing into one another?  Writer Henry Beston watched birds on Cape Cod and asked, “Does some current flow through them and between them as they fly?” We’ve all wondered that. Is there an intelligence at work? A theory popular a century ago, that a leader signals orders to the flock like a drum major at the head of a marching band, was disproved when high-speed photography made it possible to see that a flock constantly changes leaders. More recent studies have focused on mathematical chaos theory, an approach that was pioneered by zoologist Frank Heppner, who studied flocking synchronism for many years, and proposed four rules for the behavior:

1) Birds are attracted to a focal point, such as a roost, and the closer they approach it the stronger its attraction.
2) Birds are attracted to each other, because there is safety in numbers, but if they get too close, they are repelled to avoid collisions.
3) Birds want to maintain a steady velocity.
4) The path of a bird’s flight can be altered by random factors such as gusts of wind or the sudden shadow of a hawk.

When Heppner fed all four rules into a computer program and animated a collection of figures on the screen to represent birds, their motion closely duplicated actual flight behavior of flocking birds. More recently, software engineer Craig Reynolds has designed computer “Boids” that fly in simulated flocks, adding much to the knowledge of swarming birds and fish. (Watch Boids in action here.)

Of course there’s another side to all of this. We can consider all the explanations – the binary codes of behavior, the tensions of desire opposed, the need to stay close for safety but far enough apart not to injure, the various stimuli and responses, the oppositions of gravity and flight – and perhaps it helps us in a small way to understand the world, in the sense that it’s probably not bewitchment we’re witnessing or God idly stirring a swizzle stick. We’re reminded that the world is an unfolding story. This particular one includes the story of Eugene Schiefellin, the amiable lunatic who in the mid-19th century set out to transplant all of Shakespeare’s birds to America and unleashed a plague of starlings and house sparrows. It’s the story of predators and prey, of sky and field and thermal updrafts and a  horizon blowing up red at sunset, of superhighways cutting across the land, of our seldom taking the time to pull out of traffic and try to notice a thing or two.

Are patterns in nature evidence of organizing principle — or are we the principle organizer? Is order proof of Design — or an artificial system created by complex neurological systems when confronted by masses of data? Standing beside my car on the shoulder of the highway I became  aware that an entire river of phenomena was flowing around me. The face of a young woman driving past, the blare of a horn, the flash of sunlight off a windshield, the cars and semis making little windstorms that rocked my truck on its wheels – these, too, were starlings in a flock. Step back far enough and you can sometimes see a pattern, and sometimes you’ll find it beautiful.
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Richard Barnes’s book of photography, Animal Logic, comes highly recommended. It includes a stunning series of photos of starlings flocking over Rome. The patterns are similar to those I saw over the field in Michigan.

Google Images offers dozens of interesting flock photos here.