Video of a massive starling flock turning and twisting over a river in Ireland has gone viral, and with good reason. Flocking starlings are one of nature's most extraordinary sights: Just a few hundred birds moving as one is enough to convey a sense of suspended reality, and the flock filmed above the River Shannon contained thousands.

What makes possible the uncanny coordination of these murmurations, as starling flocks are so beautifully known? Until recently, it was hard to say. Scientists had to wait for the tools of high-powered video analysis and computational modeling. And when these were finally applied to starlings, they revealed patterns known less from biology than cutting-edge physics.

Starling flocks, it turns out, are best described with equations of "critical transitions" – systems that are poised to tip, to be almost instantly and completely transformed, like metals becoming magnetized or liquid turning to gas. Each starling in a flock is connected to every other. When a flock turns in unison, it's a phase transition.

At the individual level, the rules guiding this are relatively simple. When a neighbor moves, so do you. Depending on the flock's size and speed and its members' flight physiologies, the large-scale pattern changes. What's complicated, or at least unknown, is how criticality is created and maintained.

It's easy for a starling to turn when its neighbor turns – but what physiological mechanisms allow it to happen almost simultaneously in two birds separated by hundreds of feet and hundreds of other birds? That remains to be discovered, and the implications extend beyond birds. Starlings may simply be the most visible and beautiful example of a biological criticality that also seems to operate in proteins and neurons, hinting at universal principles yet to be understood.

Video: Liberty Smith & Sophie Windsor Clive, Islands and Rivers/Vimeo

Image: ad551/Flickr

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