Why Birds Sing
Red-eyed Vireo sings more than 20,000 songs a day. A Pileated
Woodpecker drums on a tree at 15 beats per second. A Wilson's Snipe dives
through the air, the feathers on its wings vibrating to produce a
winnowing sound, hu-hu-hu...
Why? Birds put a lot of effort into singing, drumming, winnowing,
and otherwise displaying. They are trying to impress mates and proclaim territories.
Now hear this
Songs are often loud and repetitive, so they tend to be noticed
more than other bird sounds. One
observer commented that a Winter Wren sings "with remarkable
vehemence," as if he were "trying to burst [his] lungs." This tiny
songster weighs just one-third of an ounce, but it sings with 10 times
the power of a crowing
rooster, per unit weight. Birds may sing their songs thousands of times
throughout the day. Dickcissels may spend as much as 70 percent of the
while establishing territories and courting females.
birds have large repertoires--the Brown Thrasher can sing as many as 2,000 distinct
songs. Other species, such as the Henslow’s Sparrow, seem to have
only one song.
In North America, we hear
mostly males singing, because they typically take the lead in defending
territories and attracting
mates. However, especially in the tropics, some species sing duets involving both the male and female.
How do scientists know why birds sing? Experiments with recorded songs have shown that birds sing to attract mates. House Wren songs broadcast near nest boxes
will attract female House Wrens, for example. Female birds
may also judge the quality of a male's song when selecting a mate. Some
studies have shown that males with extra food on their territories are
the most persistent singers, and in some species, the most persistent
singers attract females the soonest.
"Keep out!" messages
Playback experiments have also shown that songs are important in defending a territory. For example, male House Wrens respond aggressively to the recording of another male's song, sometimes even attacking the loudspeaker. In other tests, researchers temporarily removed male birds from their territories but played songs through speakers on some of the territories. Neighboring males were less likely to invade territories from which songs were broadcast, showing that song means "Keep out!" to other birds.
Song is not the only "keep out" signal that birds use. Although Northern
Mockingbirds sing complex songs on their territories during the
breeding season, they use only a loud chuck sound to declare
their winter feeding territory. Some warblers also use just a simple
call note on their winter feeding territory.
Singing on the wing
Some birds sing while in flight, especially species that nest in open areas such as grasslands or the Arctic tundra.
Western Sandpipers arrive in Alaska several days before
the females and make frequent
display flights over their territories as they utter their flight
song. Some display flights last up to five minutes and
cover the sandpiper's territory. Others are rapid
flights low over the tundra, followed by an abrupt ascent. Listen to a Western Sandpiper's flight song.
Ovenbird, a warbler of northeastern forests, sings a loud, ringing song
while perched. It also performs an aerial display at twilight or dawn.
The male chips softly, then flies 3–15 meters above the
treetops, where he hovers with spread wings while singing a rambling
flight song. Listen to an Ovenbird's song.
Male Purple Martins use a special song to attract mates. Early in the morning, the male flies hundreds of feet into the air and sings his liquid "dawnsong." Other martins up to several miles away can hear the sound. This song may attract other martins to the colony, leading to additional mating opportunities.
Many birds sing especially energetically at dawn. Researchers John Burt and Sandra Vehrencamp found that in Costa Rica, a dawn chorus of Banded Wrens involved several males that were actually listening and responding to one another in complex ways. Read more.
Drumming up a song
birds sing with their voices, others use their bills or wings to drum up a mate's interest.
A woodpecker drums on a tree to produce a
other members of the same species recognize. Woodpeckers
often select dry branches, hollow logs or other materials that provide
maximum volume for their drumming. Like songs, drumming is used in
courtship and to declare a territory.
To attract a
mate, a male Ruffed Grouse "drums" by cupping his wings and bringing
them up and forward with such force that the air compresses to emit a
thumping sound. Listen to the drumming of a Ruffed Grouse.
Wilson's Snipe “winnows” during an aerial courtship display as it
circles 300 feet in the air and dives at a speed of up to 24 miles per
hour. The outer tail feathers vibrate, producing sounds that can
sometimes be heard a mile away. Listen to the calls and winnowing of a Wilson's Snipe.
When they're not singing, birds often communicate less elaborately, using calls. More about calls.