Units of motor production: Bengalese finches interrupt song within syllables

Birdsong consists of syllables that are separated by silent intervals. Previous work in zebra finches showed that syllables correspond to the smallest motor production units (Cynx, 1990; Franz and Goller, 2002) by inducing song stops using strobe light. In this study, we interrupted the song of six Bengalese finches experimentally with the birds own song as auditory stimulus using an interactive playback approach. Five of the tested males interrupted their ongoing vocalizations within syllables (16 instances of induced interrupted syllables) in response to the playback. Additionally, we observed 9 spontaneous interruptions in our control recordings. This study establishes that birds can interrupt ongoing syllables within extremely short latencies in response to an auditory stimulus, and that auditory stimuli interrupt syllables more effectively than visual stimuli. Even if syllables are the functionally stable production units, the ability to disrupt those units differs between species and individuals, indicating various degrees of vocal control.