Eugene Schieffelin was the eccentric ornithologist who in 1890 shipped 60 starlings from London to New York City and set them free in Central Park. The next year he released 40 more, and today there are maybe 200 million starlings in the United States and Southern Canada. As immigrants go, starlings are shrewd flyers, clever mimics, and often unwelcome. The truth is they’re no more than uptown blackbirds, stocky, three-ounce grifters with iridescent blue and green plumage, along with yellow beaks and a long history of displacing woodpeckers and flycatchers, and destroying entire crops of berries and cherries. Not to mention the havoc they cause at many airports.
Ah, but when they come round in their murmurations on fall afternoons, or in early winter, what magicianry is that, gathering up out of nowhere, arriving in strands or massive clusters, over inlets or forests. You’ll see them fill up neighboring trees and fall into an oily, high-pitched chatter. Sooner or later, they settle and fall silent, like an orchestra before the first note. And then—the most subtle spooking will do it, a dog’s bark, the slam of a car door down the street, or nothing at all, and off they go at 50 miles per hour, wheeling around the countryside, sheets and sheets of them, thickening and thinning, blackening and scattering, merging and splitting, sometimes looking like a tornado cloud, or else some strange omen, and it’ll go on for 15 minutes or more, a merry band thrashing through the sky in vast clouds of star-shaped dots, like the vanishing images on a Buddha board.
The word murmuration is derived from the murmuring sound of beating wings. The performance is self-organized, cohesive, and perfectly synchronized; and distinguished by elaborate patterns of spirals, spheres, planes, and waves. What causes starlings to perform these displays? And what do they reveal about the nature of collective behavior in animals?
Theories have evolved over the last century. In 1931, Edmund Selous, a renowned ornithologist and bird activist—his older brother was the famous big game hunter Frederick Selous—wrote a book called Thought-Transference (or What?) in Birds. The notion was that birds in a flock must all be “thinking” as one; how else to explain the synchronization except by telepathy. But Selous had no evidence, only a layman’s logic. Nature panned the book and that was the end of it.
Later theories suggested that murmurations are ways to find food and keep warm. Those theories linger, but in the past 50 years the predominant explanation is predation, particularly the role of raptors, such as hawks and falcons, in triggering escape behaviors that involve particular patterns of grouping. These behaviors are also found in gulls, dunlins, and corvids. The main benefit of flocking is making it difficult for predators to single out prey.
In the mid 1960s, researchers found that murmurating birds, particularly starlings, interact—not always, but often—with six or seven of their closest neighbors, who interact with six or seven of their closest neighbors. In recent years, studies posit that a network with seven neighbors optimizes the trade-off between “group cohesion and individual effort.” One theory among researchers, in the context of predation, is that starlings are “managing uncertainty while maintaining consensus.”1 Which is to say they must fly a fine line between reacting solely to the falcon or staying within the fortress of the flock. Either way is fraught. Thus, the need to manage uncertainty.
One theory, in the context of predation, is starlings are “managing uncertainty while maintaining consensus.”
In a murmuration, the distance between fellow fliers is based on a set of rules also seen in certain kinds of fish and insects. These rules require birds to draw closer to birds farther away; at the same time, not to get too close to the nearest neighbor; and finally to join in directional flow. Add to these rules the aerodynamic factors in starlings—and the blistering speed at which the birds turn, climb, and dive—and you have a sense of the intricacy of flock synchronization.
Mario Pesendorfer, a postdoctoral research associate at the University of Natural Resources and Life Sciences in Vienna, whose work often focuses on birds, cautions about ascribing behavior to inborn patterns in animals’ brains. “When humans observe a complex global (group) pattern that arises from simple behavioral rules on the level of individuals,” he tells me in an email, “we are not very good at deciphering the individual rules. Instead, we ascribe intention, as well as other complex cognitive and behavioral processes to the animals.”
In 2019, evolutionary biologist Rolf F. Storms at the Groningen Institute for Evolutionary Life Sciences in the Netherlands, led a study on starlings that delved into the rules of murmurations.2 Storms’ interest has always been in self-organization, “where complex phenomena can be explained through the entities in the system interacting with each other through simple rules,” he tells me in an email. “That simple rules can give rise to such complexity fascinated me. I would say the most mesmerizing examples can be seen in the murmurations of starlings.”
The study, which was conducted in Rome and analyzed video footage of falcon hunting techniques, found different patterns of escape by the starlings. For example, when a falcon attacked a flock from above—not from the sides or below, and at high speed—the starlings frequently respond with an escape pattern called a “flash expansion.” The birds scatter in all directions in the sky. “But since flocking offers many benefits,” says Storms, “individuals will try to go back to their flock mates as soon as the immediate threat of being caught has lowered, which would explain the resilience of the flock against being split.” When a falcon attacks starlings at medium speed, allowing it to be detected, warnings spread through the flock, and the birds respond in a “wave.” They turn right and left, zig and zag, creating “darkened bands” that ripple through the flock, confusing the falcon. This aerial display exhibits the kind of collective intelligence that scientists see in other species, in which individuals join together to solve a single problem, in this case avoiding a hungry falcon.
Grainger Hunt, Senior Scientist Emeritus with the Peregrine Fund’s California Condor and Aplomado Falcon restoration project, underscores the fact that murmurations are emergent. “We are accustomed to seeing organized aggregations, such as groups of musicians, dancers, or soldiers, that behave as if they were purposeful units,” Hunt tells me. “The explanation is that they are directed, either by prior arrangement or by a conductor. It might likewise seem that the peregrine conducts the starling flock for the purpose of producing the effects we see from afar. But the peregrine does not purpose the shapes and movements of the flock. Nor does any starling. The spectacle of wondrous shapes and movements is an unintended effect. The peregrine is trying to catch a starling, and each starling is trying not to get caught.”
It’s evolution in the skies, the prey adopting a strategy to outsmart the predator. This unintended big dazzle is also a reminder that, often, nature’s most beautiful offerings are inspired by desperation and danger.
1. Young, G.F., Scardovi, L., Cavagna, A., Giardina, I., & Leonard, N.E. Starling flock networks manage uncertainty in consensus at low cost. PLoS Computational Biology 9, e1002894 (2013).
2. Storms, R.F., Carere, C., Zoratto, F., & Hemelrijk, C.K. Complex patterns of collective escape in starling flocks under predation. Behavioral Ecology and Sociobiology 73, 10 (2019).
Lead image: Coatesy / Shutterstock