Sparrows

A White-crowned Sparrow beginning a night of migration

Migration requires a lot of information, and birds weigh many different factors before they decide to launch into the night sky to fly hundreds of miles.

■ Much of what is known about song learning in birds is based on studies of White-crowned Sparrows. Young birds are genetically predisposed to learn the song of their own species, and to ignore the songs of other species. They memorize song patterns that they hear before they are three months old. Soon they begin to practice singing, gradually developing vocal control and refining their song until they can consistently reproduce the song model they memorized in their first few months. They will continue to sing this song, more or less unchanging, for the rest of their lives.

A White-crowned Sparrow singing

■ The song of a male Chipping Sparrow sounds like a simple trill: one note repeated rapidly on the same pitch. To us they all sound pretty much alike, but the birds are a lot more discerning. Birds can process sounds at least twice as fast as we can, so to get closer to what a bird hears we should listen to a recording at half speed or slower. In this case a simple trill is a rapid series of upslurred notes—a vocal performance that depends on exacting control and synchronization of the muscles in the two-parted syrinx (see this page). This has to be coordinated with breathing, bill position, and body movements to create a song that is precise and consistent. One study found that sparrows can sing notes with a wide range (from low to high), or notes repeated rapidly, but they can’t maximize both in the same song. We could think of a bird’s song as a kind of dance or gymnastics routine, a series of elaborate jumps, and the judges (potential mates and rivals) are looking for height and speed, along with precision and consistency.

A Chipping Sparrow singing, and a sonogram of a typical song