Look up on a fall or winter day in the Northern Hemisphere and you may see the fast, synchronous cloud of thousands of birds swirling over their roosts. While migrating south, starlings take rest stops for a few weeks at a time and perform murmurations together at dusk, sometimes lasting up to 45 minutes at a time.

The most common explanation is that murmurations are a defense against predators. But these massive flocks can also attract predators, making the phenomenon a scientific mystery.

Peregrine falcons, starlings' most common predators in North America, elicit the most elaborate murmurations. A frequent hunting strategy is to attack the flock once, suddenly and from a distance.

The flock's escape maneuvers create complex and overlapping patterns that change