The Swainson’s Thrush is best known for its distinctive, fluting song, the upward-spiraling melody that breeding males use to defend nests and territory and also probably to attract mates. While this song varies somewhat from one individual bird to the next, its whistling, constantly ascending quality is always recognizable once you’ve heard it.
Both sexes emit about a half dozen different one-or-two-note calls, none of which has the flutelike quality of the advertising song. Migrating birds utter a hollow peep or note that resembles the call of a spring peeper frog. Intruders or predators in the vicinity of a nest may hear a whit—a sharp, single note expressing alarm or the intention to distract. The bird may repeat this note to try to lure a human intruder away from a nest, and it may respond to a human imitation of the sound. Swainson’s Thrushes also have a thin, high-pitched, single-note whine similar to that of American Robin. They also make a bink like water dropping onto a hard surface, and a single, drawn-out, metallic peeer reminiscent of the song of the Varied Thrush, but not as long.