Why Do Birds Sing?

What was the world's first music?

Chances are it was for the birds.

Birdsong is older than the oldest human music, perhaps millions of years older. Could a songbird's sweet, clear melody have prompted an ancient human to carve out a flute and start blowing? Certainly birds have influenced some very famous composers: Mozart is thought to have been inspired by the song of a pet starling, and Beethoven's sixth symphony imitates the sound of the nightingale.

Of course, not all birds sing. Vultures make no noise at all. Other birds, such as storks and pelicans, don't make much. Many birds make short, simple sounds known as calls. But only the birds known as passerines, or songbirds, actually sing. Among the 5,000 kinds of songbirds are many birds you may know, such as robins, sparrows, cardinals, blue jays, and even crows.

Some birds, like the nightingale, make songs that are music to our ears. Others, like the three-wattled bellbird, belt out songs that sound more like car horns honking than flutes playing. Still, however odd a song may sound to human ears, it works well for the bird that sings it. Short songs, repeated over and over, are more likely to be heard clearly in dense forest than long, complicated songs are. Buzzing songs travel better across open meadows and grasslands than whistling songs. And the bellbird's honk? It's perfect for the rainforest, where the loud hum of insects would drown out a more delicate melody.

Scientists have long been fascinated by birdsongs, but until about 60 years ago it was difficult to study birdsongs carefully. With no way to record and play back the songs, scientists had to write them down as they heard them, using the alphabet or musical notes. This was a problem because everyone heard a bird's songs differently. Did the black-capped chickadee's song sound like "Fee, bee, bee" or "Hey, sweetie" or something else entirely?

Then, with the invention of portable tape recorders, the study of birdsong blossomed. Now scientists can record songs in the wild and listen to them later, slow the songs down, or even play them back to other birds and see how they react. They've used their new tools to learn more-and raise new questions-about how and why birds sing.

So Why Do Birds Sing?

Songbirds use both calls and songs the way we use language: to communicate with those around them. Calls, which can be heard all year round, communicate short, simple messages, like "Mom, I'm hungry" (Cheep! Cheep!), "Where are you?" (Honk! Honk!), or "Watch out! A hawk!" (See! See!). Songs are usually longer than calls and more complicated-and they're usually performed only by males and only during the nesting season. A male songbird uses its songs for the two most important things it does: defending its norm or territory, and finding a mate.

A bird's territory should have plenty of food and water, a safe place to build a nest, and materials to build the nest with. When a bird finds a good territory, it doesn't want to share with other male birds of the same species (different kinds of birds can share a territory because they eat different foods and pick different nesting sites). A song can warn other males to keep out or risk a fight.

In one experiment using great tits, yellow and black birds common in Europe and Asia, scientists removed all the males from an area and played recordings of a male great tit singing. Other males heard the song and wouldn't enter the territory-until they figured out that a tape recorder, not a real bird, was doing the singing.

Songs can also signal when an intruder is near. If a male black-headed grosbeak is late getting back to the nest, the female sometimes imitates a male singing. Her partner thinks another male is trying to take over his territory, so he flies back quickly-tricked into taking his turn on the eggs!

Some birds engage in singing duels, called countersinging, to decide who gets a choice territory. One bird sings a song, the second answers with the same song or a variation, back and forth until someone wins. How does the winner triumph? Perhaps he can sing longer without getting pooped. Or he might just know more songs.

The best territory isn't much use without a mate to share it with, and a songbird depends on its music to attract females. In another experiment, scientists set out dummies that looked like male flycatchers. Half the dummies played a recording of the flycatcher's song. Females flocked to the singing dummies but ignored the ones that were silent.

How Do Birds Learn Their Songs?

Baby birds are born knowing the calls that mean "I'm hungry," as well as all the other calls they need to survive. But what about songs? Are babies born knowing those too?

To find out, a scientist hatched some male chaffinches and raised them in a lab, away from other birds. Some of the birds were allowed to hear recordings of adult chaffinches singing. When those birds grew up, they could sing the chaffinch greatest hits perfectly. But babies who didn't hear recordings of adult males singing never did learn to sing like chaffinches. Instead, they chirped disorganized bits of sound.