The smallest songbird in North America is the verdin, a species of penduline tit. Other small songbirds include the American bushtit, all species of sparrows, warblers and wrens, the American goldfinch, the chickadee, the kinglet and the indigo bunting.
Songbirds are also called passerines, or perching birds, because their three-toed feet are adapted to gripping a perch. They are the dominant species of landbird on all continents, comprising about 50 percent of all bird species on Earth. North American songbirds range in size from 2.5 pound ravens to tiny kinglets and wrens, which weigh only about a third of an ounce.
Songbirds have several characteristics that differentiate them from other birds, including a highly developed voice box, which is what allows them to create complex sounds. The most complicated songs are produced by thrashers, thrushes and wrens. The brown thrasher is thought to be capable of making over 2000 unique sounds.
Passerines have large brains in relation to their size. Members of the corvid family, such as crows, jays and ravens, are thought to be among the most intelligent animals on Earth aside from humans. These large birds are able to mimic many sounds, including human words and the sounds of cats and dogs. They also exhibit a high capacity for learning and complex problem solving skills.