What is the term for the large, swirling flocks of starlings seen at dusk?

The large, swirling flocks of starlings seen at dusk are called murmurations.

A murmuration is a synchronized aerial display in which many starlings twist, expand, contract, and change direction almost as if they were a single organism. The flock does not need a leader issuing commands. Instead, each bird responds rapidly to the movements of nearby neighbors, allowing coordinated patterns to spread across the group.

Murmurations are most often seen near communal roosts, especially in autumn and winter before sunset. Their sudden, fluid movements may help confuse predators such as peregrine falcons and sparrowhawks. The flock’s shape can change in seconds, producing the dramatic silhouettes often associated with the phenomenon.

The word is linked to the low, indistinct sound made by many birds flying together. A murmuration is more specific than a congregation or ordinary flock: it describes the flock’s collective swirling behavior, not simply the presence of several birds. In Denmark, immense starling gatherings are traditionally known as sort sol, or “black sun.”