What Makes Starlings Gather?

Humans are unquestionably captivated by the hypnotic gatherings of hundreds or thousands of starlings in pulsing murmurations (simply check the number of views on Youtube). But the swirling avian bodies provide far more than our entertainment—they likely help the birds survive. Scientists are trying to decode these phenomena to better understand what benefit birds reap from the morphing mass, and are finding that the mesmerizing displays may be as protective as they are gorgeous.

It’s widely accepted that murmurations offer safety by virtue of their sheer scale. For birds within the mass, the center likely represents the ultimate escape from predators on the fringe. Some researchers think it’s this constant quest for centrality that puts the murmuration in a state of permanent flux, as birds continuously fine-tune their flight to reach the safest possible position. This creates an unpredictably fluid body, devoid of a central point.

“Hiding” in such a noticeable swathe may seem counterintuitive, but the gathering also means birds have hundreds of eyes watching out for predators, rather than just two: Research has shown murmurations can detect predators more quickly than solitary birds.

So what does the flock do when it spots a predator nearby? New research reveals that the dark ripples that often pass through portions of the avian cloud may help starlings evade predators—but not in the way we might think.

Called “agitation waves,” the motions occur when a predator like a falcon gets too close to the crowd, triggering a fast moving ripple that travels at almost 44 feet per second across the mass and away from the offending bird. From afar the starlings appear to be moving closer together.

But using a program called Star Display to model these murmurations, Charlotte Hemelrijk from the University of Groningen realized the birds aren’t actually getting closer. They’re simply rotating to reveal the broad side of their wings. “This exposes a larger area of the wing temporarily and this is seen by us as a dark band,” Hemelrijk says. The angled bodies look momentarily like a solid mass and consequently, individual birds are tougher to pick out.

Just as it deceives us, this illusion might throw off predators, momentarily stunned by the change. “It confuses the predator as to whom it should attack,” Hemelrijk says.

In addition to safety, these large gatherings also offer warmth, and a chance to feed collectively. Compared with solitary flight, it’s no wonder birds join in, inadvertently creating a spectacle for those of us below. 

Watch a murmuration: