Fall is time for pumpkins, spiced latte, and leaf peeping, and also when we can start spotting huge pre-dusk bird flocks which swirl through the air in mesmerizing murmurations. These shape-shifting, cloud-like flocks (check YouTube for many amazing videos) appear to defy the laws of physics, and while the birds’ quick movements may seem planned or coordinated, there is no orchestrating leader. The birds dip and dive randomly, somehow without crashing into one another.
Mathematicians recently studied individual bird movements within a murmuration and noted that a flock behaves like a soft crystal, with each animal serving as an evenly spaced "atom" in a lattice-like formation. The glue holding that crystal together is air itself. Each bird in a single-file line leaves a trailing wake, and the bird behind uses those swirling vortices to keep its distance. Drift too close and air pressure nudges it back, fall too far behind and the flow draws it forward into the ideal spot. The structure remains “soft” which allows a flock to bend its shape around a hawk or a building without breaking formation. One researcher noted: “Lines of birds… behave like an elastic material with regularly spaced individuals held together by flexible, or spring-like bonds…”