How pigeons give falcons the slip — A Peregrine Falcon dive-bombing at several hundred miles an hour to knock a pigeon out of the sky would seem to be a study in single-mindedness. At those speeds, attention must be paid. But even a falcon in hot pursuit can become distracted. And what distracts it, is a patch of white feathers on the rump of an otherwise blue-gray pigeon. “The brain can be primed by a conspicuous thing,” said Alberto Palleroni. The falcon, he said, sees the conspicuous thing — the white patch — and doesn’t notice the pigeon starting to turn away and escape. “In effect, it’s a kind of a card trick or a ruse” on the part of the pigeon, Palleroni said.
Palleroni et al. (2005) observed more than 1,800 falcon attacks on wild pigeons over seven years. They recorded the plumage types among the pigeons and noticed that while birds with white rump patches made up 20% of the pigeon population, very few were captured by the falcons. When a Peregrine Falcon attacks a pigeon, it plunges at speeds greater than 200 miles an hour, levels off and comes upon the pigeon from behind, punching it with what amounts to a closed fist. At those speeds even a grazing blow kills the pigeon; the falcon then circles back and picks it up. The only way the slower-flying pigeon can escape is by dipping a wing, rolling and veering off. If the falcon is distracted by the white patch, it won’t notice the dipping of the wing (which, being blue-gray, blends with the landscape) until it’s too late.