What the flock is up with murmurations? And what's the difference between a swarm, a herd, a school, and a flock? In this first of a two-part episode, Bill and Steve explore the world of collective behavior, and take a specific look at murmurations of the European Starling (Sturnus vulgaris). This species gathers in large flocks (sometimes numbering into the tens of thousands!) that dive and swoop across the sky, creating beautiful, shifting forms that delight, amaze, and mystify. Researchers from numerous fields study these formations, and this month, the Field Guides share the latest research into this stunning natural phenomenon.