The music of wild birds is among the most glorious gifts of nature. It inspires us not just to be bird-watchers, but to be bird listeners as well. When we listen closely, this music arouses our curiosity. It makes us ask questions.
Why do some kinds of birds always sound pretty much the same, while individuals of some other species sound recognizably different? Why do some birds sing the same song over and over, while others seem to show off with varied playlists? To better understand, let’s take a look at the way birds learn their songs in the first place.
Bird Songs vs. Calls
Most of our familiar backyard birds, from thrushes and jays to orioles and goldfinches, are classified as songbirds. But many of the sounds they make are not considered songs at all. In fact, the sounds you hear regularly are usually considered calls.
Think about songs for a minute so you can compare. Bird songs tend to be more complex and melodious than calls. Typically, only the males sing during nesting season, because they’re trying to establish their territories and attract mates. By comparison, calls are usually short, simple sounds, and the birds use them all season. Flocks of American robins, for example, make a wide variety of clucking, chirping or lisping calls at any time of year. But when a male robin perches in a treetop at dawn in spring and says cheerup cheerily cheerio cheerup for an hour, that’s a song.
Scientists know about another fascinating difference between calls and songs. Among most of the true songbirds, the calls are instinctive, so the birds are born with the ability to make them. But the songs are learned. Before it can sing, the young bird must hear the songs of its own species during the first few months of its life. If it were possible for an indigo bunting, for example, to grow up without ever hearing its own kind, it would make normal calls, but it would never develop the ability to sing its species’ distinctive song.
How Birds Learn Their Songs
Even in the learning of songs, though, instinct plays a part. The young bird has the natural ability to recognize the songs of its own kind. The heartbeat of a young song sparrow will actually speed up when it hears a male of its own species singing; it doesn’t react this way when it hears another kind of sparrow.
So we could say that the bird has a built-in template for learning the right song. Still, it must hear the song while it’s young. After the first few months of life, it’s often too late.
A typical songbird goes through four stages. First there is the critical learning period, when it must hear the songs of its own kind. Then there is a silent period, often several months, during which those songs are simply stored in its memory. Then the bird enters the subsong period, when it starts to experiment with soft, rambling versions of the song, much the way a human baby babbles. Finally, there’s a period of a few weeks when the bird perfects its performance, putting the syllables and sounds together into a typical song for its species.
It’s also important to note that some birds continue learning new songs all their lives. This is especially true for birds that mimic the songs of other species. While we were writing this article, a starling in the maple tree in front of our house was doing perfect imitations of bluebirds, kestrels, meadowlarks, flickers and a dozen other kinds of birds. Mockingbirds are famed—and named—for their ability to mimic all kinds of birds, as well as doorbells, phone ringtones and other new sounds they hear throughout their lives. Other mimic birds that can fool the ear include catbirds, parrots and lesser goldfinches.
Regional Bird Songs
Because a young bird tends to learn the songs of its immediate neighbors, the locals all might sound pretty much the same. But the same species can sound very different in another region, so birds, like humans, may have local dialects. The song dialects of white-crowned sparrows have been studied for decades. In some places, such as parts of the Pacific Coast and the Canadian Rockies, the song patterns of white-crowned sparrows may change noticeably every few miles, and someone who knows the local birds well may be able to tell exactly where they are just by listening to the sparrows!
Although a young songbird has an instinct for recognizing and learning the song of its own kind, this instinct is not infallible. Sometimes a bird will learn the song of the wrong species. We have occasionally run across this—for example, a prairie warbler that perfectly sang the song of a field sparrow. Sometimes these seeming mistakes have a practical side. Where the ranges of black-capped chickadees and Carolina chickadees come together, a male may learn and use the songs of both species to drive all possible rivals out of his territory.
Although most typical songbirds learn their songs, there are other kinds of birds for which all the sounds are based on pure instinct. Mourning doves, for example, instinctively know how to make their mournful cooing. Members of the flycatcher family, such as phoebes, wood-pewees and kingbirds, also know their songs by instinct, and will develop the right song even if they don’t get to hear their own kind.
One of the best examples is the brown-headed cowbird. Female cowbirds lay their eggs in the nests of other birds, so the baby cowbird is always raised by other species. But it somehow knows that it’s a cowbird, and regardless of what it hears as a nestling, when it grows up it will sound just the way it should!
Learning more about how birds tune up their vocal instruments can enrich our appreciation of nature’s symphony. The next time you’re out and about, listen to the birds for a few minutes and see what you can pick out and learn.