VOA常速英语:Scientists Unlock Mystery of Bird Flocks

How can flocks of birds, schools of fish or herds of antelope suddenly change direction -- all the individuals adjusting their movement in concert, at seemingly the same time? British researchers now have some insights into this behavior, which has puzzled scientists for a long time.

A large flock of starlings performs its endless random dance above a beach in southern England, constantly changing direction as if commanded by a leader. Their movements resemble an organized structure -- but careful observations fail to identify the one bird that all the others follow.

A group of scientists at the University of Warwick say that's because of birds' instinctive need to maintain optimal density of the flock, in order to be able to see through it and watch for predators, while keeping the flock together.

The lead researcher of the study, Daniel Pearce, said every bird in the flock has the same set of information.

“So it's like lots of individuals independently choosing to behave in a way that from the outside looks like a very organized structure, but it's actually lots of individuals doing the same thing at the same time,” said Pearce.

Starlings' flight

In video recordings, starlings pursued by a predatory bird showed similar behavior,

This was further confirmed by a computer model algorithm simulating a flock of starlings in flight.

“Because the flock is always marginally opaque, the individuals are more likely to be able to see the predator, they're more likely to see the responses of other birds to the predator, and also because they're always trying to keep this high information within their view they always come back together, so the predator is unable to permanently split the flock up,” said Pearce.

Schools of fish

Physics professor Matthew Turner said what works in the air could work in the water.

“Fish are a little bit different to birds, in that they have other senses. They can measure pressure, for example, but basically they're still visually-based organisms. They look at one another as they move, so we are optimistic that a very similar model could also explain the behavior of fish,” said Turner.

Scientists say understanding the behavior of birds may help them create algorithms to direct flocks of small robots, tasked with forming certain shapes or objects.