A flock of starlings is called a murmuration. A new viral video is making people wonder how they do it. (Photo: Shutterstock)

A two-year-old video of a murmuration — a flock of starlings — is going viral, and now everyone is asking how the heck they learned to dance across the sky like a screensaver. Before we dig into the science, you have to watch this video. It was apparently shot from a river in Ireland as a pair of girls went for a canoe ride. Enjoy the music. Then keep reading.

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Where do murmurations rehearse? How does each starling know when to turn? And who's the brains of the operation? Murmurations gather all over the world, pretty much everywhere except Asia and South America. But starlings are native Europeans, and that's where their numbers remain the highest. When starlings go to sleep, they prefer not to be alone. In some neighborhoods in England, the roost sizes can vary from the thousands to well past 1 million, according to Amazing Animals of the World. Roosts are loud and eerily populous, in an Alfred Hitchcock kind of way.

Occasionally all the birds get up and stretch out their wings in perfect unison. They've been doing this for hundreds of years, but only in the last few have scientists been able to answer fundamental questions about how their patterned flight behavior works, mechanically speaking. In the 1970s, scientists were relying on still photos of birds in flight to try to guess at their behavior. What they found was somewhat revealing: In transit, individual birds flying in unison managed this simply by constantly avoiding collision. Generally, they were taking their lead from the bird directly in front of and below them, rather than the birds to the sides or above.

In 2008, researchers in Rome published a paper in the journal Animal Behaviour in which they analyzed high-quality video footage of 2,700 starlings in flight. They noted that individual birds keep a minimum distance from their neighbors, proportional to their wing spans. Other research that year using similar analysis revealed that individual birds in flight coordinate their movements based on observations of six to seven birds around them.

As Wired points out, this mechanism has more to do with physics than biology. Murmuration flight depends on the same principle that underlies a phase transition of a solid to a liquid or that some physicists say could cause the collapse of the universe. The molecular behavior of a body — whether it's ice in a hot room or a murmuration in flight — changes until it reaches a point where it can no longer exist in its current form. It becomes something else. It melts; it turns left.

The journal Behavioral Ecology published research in 2010 that used even better models for starling swarms. These virtually proved that the birds were relying on their neighbors for information. But why were they dancing in the first place? Research on that question is scant, but it probably has more to do with survival than ballet.

One 2011 study in Animal Behaviour looked at what happened when a peregrine falcon started chasing the murmuration. The scientists found that waves of faster and more dense birds swept outward from the predator. Subsequent research using robotic birds found that smaller birds that flew closer together and had better eyesight (all characteristics of starlings) could move more suddenly and gracefully. Studies have also shown that flocks are more dense around the edges and less so in the center. All of this would seem to improve their ability to respond to a threat.

Don't let this ruin the fun, though. Most of nature's beauty has to do with one of two things: sex and being eaten alive.

Above photo courtesy of Shutterstock

Murmuration from Islands & Rivers on Vimeo.