Nonvocal Sounds

photographs of a Northern Flicker and Anna's Hummingbirds by Rohan Kamath
When we think of bird sounds, singing is the first thing that comes to mind. But many birds have found other ways of generating acoustical signals to serve functions usually accomplished by songs. Some bird sounds used in territorial and courtship displays are produced with their bills, feet, wings, or tails. Many songbirds clack their bills, but otherwise the use of such sounds in displays is limited primarily to species with poor singing abilities and occurs infrequently among the passerines.

Mated storks and albatrosses often communicate with bill clattering and bill tapping, but the best-known use of bills to produce auditory displays among North American birds is the drumming of several woodpecker species. Both sexes engage in loud rhythmical drumming by striking their bills against a hollow or dried branch or, to the annoyance of many homeowners, metal gutters, stovepipes, drainpipes, and even trash cans! In the Yellow-bellied Sapsucker, Northern Flicker, Downy Woodpecker, and Hairy Woodpecker, drumming functions much as song does to proclaim territorial boundaries and to attract mates.

By altering the spacing of wing or tail feathers and causing them to vibrate, birds can create a variety of whistling, rattling, buzzing, or other sounds as air passes through those feathers in flight. These sounds are evident in the courtship displays of the American Woodcock, Common Snipe, several swifts, and in the booming sound of Common Nighthawk flight. Sound made by the two wings or their carpal bones actually striking each other occur in the display flights of Short-eared and Long-eared Owls. One of the best-known woodland sounds of spring, the drumming of male Ruffed Grouse, is performed from a low perch such as a fallen log. The sound is produced by the cupped wings of the male grouse striking the air as he flaps them forward and upward. Grouse drumming serves for both territorial defense and mate attraction and is easily detectable as much as a quarter of a mile away.

Males of the eight hummingbird species that breed widely north of the Mexican border employ wind-and-feather-derived sounds in their territorial and courtship displays.
Male Broad-tailed Hummingbirds use a shrill wing whistle when defending courting territories. Birds experimentally silenced by placing a thin film of glue on the tips of the noise-making primary feathers defended their territories less effectively. Presumably they could not communicate threat and were generally less aggressive because they did not hear their own buzzing flight.

The most spectacular courtship sound of hummers is the explosive noise made by a male Anna's Hummingbird at the bottom of its U-shaped dive as it passes near a perched female. The name "hummingbird" was acquired from the early English colonists who knew only the Ruby-throated Hummingbird of the east with its buzzing flight. The majority of hummingbird species, however, produce only relatively inconspicuous flight sounds, and instead use song to a much greater extent in their courtship display.
SEE: Visual Displays; Vocal Functions; Bills.
Copyright ® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.