Look up on an autumn or winter day in the Northern Hemisphere and you might see the fast, synchronous cloud of thousands of birds swirling over their roosts. As they migrate south, starlings take rest breaks for a few weeks at a time and perform murmurations together at dusk, sometimes up to 45 minutes at a time.
The most common explanation is that murmurations are a defense against predators. But these huge herds can also attract predators, making the phenomenon a scientific mystery.
Peregrine falcons, the most common predators of starlings in North America, elicit the most extensive murmuring. A common hunting strategy is to attack the herd once, suddenly and from a distance.
Simulation of a murmuration
The herd’s flight maneuvers create complex and overlapping patterns that quickly change in density and shape. Each escape pattern depends on the threat level and the pattern that preceded it. Read more about what we know about starling murmurs.
Wave events, in which the birds roll through the air, confuse the attacker. The darker pulse seen during a wave event reflects a change in the way the starlings’ bodies are oriented, rather than an increase in density.
There is no leader in a murmuration – the flock acts as a single entity. To remain united through the different escape patterns, each bird follows and mimics the behavior of seven neighbors. By focusing on a fixed number of birds, the group can quickly adapt, become dense or sparse, change shape, or even split in two – all while staying together.
Starlings’ peripheral vision helps to track other herd members and look for predators.
The falcon’s surprise attack produces the best results, especially if it manages to force a bird to move away from the flock. While stragglers are relatively rare, predators are much better at catching this single bird than a group.
Diana Marques and Kennedy Elliott, NGM Staff. Videos: Nick Dunlop. Sources: Charlotte Hemelrijk, University of Groningen; Andrea Cavagna, National Research Council of Italy; Melanie Haiken; Shannon Butler et al. Social birds copy each other’s lateral scans while following group mates with poor vision. Animal behavior