A couple of years ago, I was riding on a train through the German countryside with my family. Out of the fields next to us rose a flock of what must have been several thousand birds, who then executed some of the most beautiful aerial maneuvers I have ever seen, shaping and reshaping a series of organic, flowing patterns against the grey background of clouds. I felt privileged to have been a witness.
So, imagine my delight when the latest issue of Physics Today showed up in my mailbox with the following cover:
There’s a lovely two page article on the STARFLAG project, which is modeling the 3-dimensional flocking behavior of starlings outside of Rome, using 3-d stereograms. The pictures are just spectacular, and give some sense of why I was mesmerized on that German train:
They’re coming up with interesting results about how the birds must be making individual decisions within the flock. They get the best match to the observed behavior by assuming that the birds track their 6-7 nearest neighbors, regardless of local density. (This idea is familiar to astronomers, who frequently use N-th nearest neighbor statistics when estimating density, rather than averaging over a fixed distance.) The distribution of nearest neighbors also seems to be anisotropic, with a tendency to find the nearest neighbors to the sides, where the birds eyes are. Biologists have reached similar conclusions based on models of schooling behavior in fish. However, the STARFLAG project is being led by theoretical physicists at the National Institute for the Physics of Condensed Matter in Italy, so you can imagine that the methodologies are a bit different from what biologists would naturally pursue.
Update: I’m daring to embed a video:
Update on the Update: There’s a longer, informative video here with somewhat better footage. It really picks up in the second half.