# How a Flock of 400 Flying Birds Manages to Turn in Just Half a Second

## The birds’ patterns of movement are surprisingly similar to that of superfluid helium

smithsonian.com

A flock of starlings preparing to roost for the night is an awesome spectacle. Thousands of birds move in unison, creating a dynamic cloud of living creatures. Now, researchers have gotten at the mathematical heart of what makes those intricate aerial dances possible. Water, it turns out, is a better behavioral analogy than gas.

Researchers previously assumed that birds in a flock maintain a certain distance apart from one another, and that once a decision is made by one bird, it diffuses through the flock like gas, the New Scientist reports. Italian researchers analyzed the movements of starling flocks using a series of high-speed cameras that could track individual birds as they performed aerial acrobatics in unison.

The researchers found that a few birds clump closely together, and they are the ones that call the shots when it comes to turning, the New Scientist continues. However, there is no designated leader team; instead, the birds take turns. Once those birds begin to turn, the message spreads fast: about 20 to 40 meters per second, ScienceNOW reports, meaning a flock of 400 birds needs just about half a second to turn.

Here's ScienceNOW with more on how the birds are able to pull that off:

The researchers derived a mathematical description of how a turn moves through the flock. They assumed each bird had a property called spin, similar to the spins of elementary particles in physics. By matching one another's spin, the birds conserved the total spin of the flock. As a result of that conservation, the equations showed that the information telling birds to change direction travels through the flock at a constant speed—exactly as the researchers observed. It's this constant speed that enables everyone to turn in near-unison, the team reports online today in Nature Physics.

Algorithms that describe the flock's behavior, the researchers found, closely resemble those of superfluid helium, nicely demonstrating the fact that shared mathematical and physical principles permeate all facets of the natural world, ScienceNOW writes.