Why do flocks of birds dive and whirl together in the sky? A biologist explains the science of whispers

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Why do flocks of birds dive and whirl together in the sky? – Artie W., 9, Astoria, New York

A flock of thousands of shape-shifting starlings, called murmuration, is amazing to see. No less than 750,000 birds come together in flight. Birds disperse and congregate. The herd separates and merges again. The murmurs constantly change direction, rising a few hundred feet, then tumbling down to almost crash to the ground. They look like swirling spots, forming teardrops, figure eights, columns, and other shapes. A whisper can travel fast – starlings fly up to 50 miles per hour (80 kilometers per hour).

The European or common starling, like many birds, forms groups called flocks when foraging or migrating. But a whisper is different. This particular type of flock is named for the low murmuring sound it makes from thousands of wing beats and soft flight calls.

The murmurs form about an hour before sunset in the fall, winter, and early spring when the birds are close to where they will roost. After perhaps 45 minutes of this spectacular aerial spectacle, the birds all drop to their roosts for the night.


Why do starlings murmur?

Unlike the V-formations of migrating geese, whispers offer no aerodynamic advantage.

Scientists believe that a whisper is a visual invitation to attract other starlings to join a nocturnal roost as a group. One theory is that spending the night together keeps starlings warmer because they share body heat. It could also reduce the risk of an individual bird being eaten overnight by a predator such as an owl or marten.

This dilution effect could be part of the reason the murmurs occur: the more starlings there are in the flock, the lower the risk of a bird being the one caught by a predator. Predators are more likely to grab the nearest prey, so the whirlwind of a whisper can occur as individual birds attempt to move towards the safer middle of the crowd. Scientists call this the selfish herd effect.

Of course, the more birds there are in a flock, the more eyes and ears there are to detect the predator before it is too late.

And a gigantic mass of swirling, whirling birds can make it difficult to focus on a single target. A falcon or falcon can be confused and distracted by delicate wave patterns in the whisper’s movements. You also have to be careful not to collide with the herd and injure yourself.

More than 3,000 volunteer citizen scientists reported spotting whispers in a recent study. A third of them saw a raptor attacking the whisper. This observation suggests that murmurs form to help protect the birds from predators – but it’s also possible that a huge murmur was what attracted a hawk, for example, in the first place.

How do starlings coordinate their behavior?

Whispers have no leader and follow no plan. Instead, scientists believe the movements are coordinated by starlings observing what others are doing around them. The birds in the middle can see through the flock on all sides to its edge and beyond. Somehow they keep track of how the herd as a whole is moving and adapt accordingly.

To find out what is going on inside the whispers, some researchers film them with several cameras at the same time. Then they use computer programs to track the movements of individual starlings and create 3D models of the flock.

The videos reveal that the birds aren’t as dense as they might appear from the ground; there is room for manoeuvre. Starlings are closer to their side neighbors than those in front or behind. Starlings on the edge frequently move deeper into the flock.

Mathematicians and computer scientists are trying to create virtual whispers using rules that birds might follow in a flock – like moving in the same direction as their neighbour, staying close and not colliding. From these simulations, it looks like each bird has to follow seven neighbors and adapt based on what they’re doing to keep the whisper from collapsing into a chaotic mess. And they do all of this by flying as fast as they can.

Large schools of fish can appear to behave like whispers, as can groups of certain swarming insects, including bees. All of these synchronized movements can happen so quickly in herds, herds, swarms, and schools that some scientists once thought it required animal ESP!

Biologists, mathematicians, physicists, computer scientists and engineers are all working to understand how animals perform these displays. Curiosity drives this research, of course. But it can also have practical applications, like helping to develop autonomous vehicles that can travel in close formation and work in coordinated groups without colliding.

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This article is republished from The Conversation under a Creative Commons license. Read the original article here: https://theconversation.com/why-do-flocks-of-birds-swoop-and-swirl-together-in-the-sky-a-biologist-explains-the-science-of – whispers-176194.

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