It is midwinter at Alexanderplatz station in Berlin. A single starling hops along the platform, between the McDonald’s wrappers and empty beer bottles. Suddenly, it lifts off—black wings glinting blue and green—to join hundreds of its kind dancing against the pink evening sky. 

A murmuration of starlings is one of the great joys of winter. This spectacle of collective movement can feature anything from a few hundred to hundreds of thousands of birds, all whirling with liquid synchronicity. As bird-watcher and author Tim Dee writes in The Running Sky, it resembles “iron filings made to bend to a magnet,” each bird closely monitoring the flight of its neighbors and reacting in milliseconds to tiny changes in direction. For the starlings, these gatherings have a practical purpos...