What is a starling thinking?

A murmuration can run to hundreds of thousands of birds, and there is no leader. Each starling tracks about seven neighbours and matches them, which is enough for a change at one edge to sweep the whole flock in under a second.

The flocking is anti-predator. A peregrine struggles to lock onto one bird inside a shifting mass, so the shapes people photograph at dusk are a defence rather than a display.