Feathered Noisemakers: How Birds Communicate Without Singing

Virtually everyone knows that songbirds communicate by singing. Less well known is that many birds can communicate just as well by making other kinds of sounds, without using their voices at all. The birds' noisemaking instruments may be limited, but the resulting sounds are incredibly varied and communicative.

Not surprisingly, many birds use their powerful wings as noisemaking instruments. One of the most remarkable examples is the courtship performance, serving as both an invitation to females and a challenge to competing males, by the male ruffed grouse. Standing usually on a log and bracing himself backward on his tail, he brings his cupped wings forward and upward and then back again in quick beats. Starting slowly with measured thumping, he increases the speed till the sound reaches a climax as a thunderous whir, at which point he stops.

Researchers call this action "drumming," but in fact the grouse strikes only air. The noise is so loud that people can hear it a quarter of a mile away. Drawing so much attention to itself is normally dangerous for a bird, especially one on the ground. However, the great horned owl, the grouse's main enemy, rarely kills a drumming grouse. The reason for that safety is that the grouse's drumming is pitched below the owl's hearing range, so no matter how loud the sound gets, the frequency (cycles per second) is too low for the owl to hear it.

More common than wing noises produced by drumming are those produced by flying. The male nighthawk, in his courtship flight, plunges earthward, and as he reaches the bottom of his dive, he produces a booming sound as the wind bursts through his wing primaries. The noise resembles the sound made by a person blowing across the top of an empty bottle.

The male short-eared owl is usually a quiet flier. But in his courtship flight, he suddenly dives and simultaneously produces a clapping sound with his wings by stretching them in back of his body and slapping them together in short strokes. After reaching the bottom of his dive, he goes back up and repeats the maneuver.