TOO SOON TO panic

Are false-alarm flights beneficial?

- PETER RYAN

To flee or not to flee...? Red-billed Queleas flock tightly to evade a Yellow-billed Kite. The 'fire-drill' hypothesis proposes that the frequent false-alarm flights by foraging flocks of birds help to prepare them for the real thing.

Many birds feed in flocks to reduce the risk of predation. By doing so, they benefit in three ways. First, because there are more eyes scanning for threats, the probability of detecting an approaching predator increases with group size. A linked benefit of this collective vigilance is that by having others to help spot predators, birds in flocks can spend more time feeding.

Secondly, by forming a cohesive group that twists and turns together in flight, flocking birds confuse predators, reducing their success. And thirdly, even if the predator succeeds in killing one member of the group, the risk of predation to any one individual decreases with group size. For group foraging to persist, these benefits have to outweigh the potential disadvantages, such as competition for food and the distraction of social interactions.