Just like we must learn to talk, birds learn to sing. They listen to their parents and try to imitate them, often stumbling through meaningless noises like a babbling infant before honing their technique.
And just as humans learn French in one country and German in another, some bird species have been found to have different song languages as well.
The white-crowned sparrows along California's coast live in clearly defined territories, each with a distinctive dialect. These sparrows rarely cross territory lines, interacting and breeding only with others that sing the same language, a habit that might eventually divide the birds into different subspecies.
Does bird song constitute a language the same way English does? Probably not. Still, some species make an enormous variety of sounds--the brown thrasher, for example, has over two thousand songs in his repertoire.
Singing To Attract
Most of this singing has to do with establishing territory or attracting a mate, but birds also use their voices to convey information about food sources, flocking, parent-young relationships, and predators. Sometimes mated pairs will develop a song, or even a tight duet, that is unique to that pair.
One study cataloged all the sounds from a group of nesting crows. In addition to the shared songs, it turned out that each bird had a distinctive sound that only it made.
This sound functioned something like a name. If a bird's mate was absent, the bird could summon it back by uttering the mate's distinctive sound. Birds continue to surprise us with the interesting ways they communicate, but the book is far from closed on the fascinating topic of bird song.