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.