Birds Flocking for Protection

The birds flocking at your feeder scatter almost instantly when a Sharp-shinned Hawk flies over. Though only one might actually seen the hawk, all react. This scene illustrates how valuable feeding in a flock can be in avoiding a predator. In a flock, there are many eyes, which means each bird can spend more time feeding and less time looking over its shoulder.

Being in a flock helps avoid predation in other ways too. For a bird in a big flock that is attacked by a hawk, probability alone makes it less likely that a particular individual will be the victim taken. This is small solace to the captured bird, but a benefit to all the others. Another benefit is the factor of danger and confusion a mass of flying birds presents to a predator. Imagine the challenge of picking a single Western Sandpiper out of a flock of a hundred or a thousand birds, all wheeling rapidly in tight formation. The effect must be confusing and bewildering, and the predatory bird is likely to be frustrated unless it can isolate a single individual.

Within the flock, some places are safer than others. Birds that can remain at the center of the flock are less likely to be picked off by a predator than those who are flying at the edges. The importance of being at the center of the flock makes flock behavior all the more coordinated. Any available space within the flock gets filled by birds at the edge, and birds are unlikely to stray beyond the edges of the flock. Sandpipers whirling in tight formation over a bay provide a spectacular ballet for anyone who watches. They achieve their coordination quite simply.

Each bird pays attention to the few birds beside it, just as dancers in a chorus line. When the bird in front turns, the rest turn. Thus, even though it looks as if the whole flock turns in unison, each time the flock changes direction it does in a progressive wave -- first one birds, then another, and then another. But the members of the flock react to each other so rapidly that it looks as if the turn takes place all at once.