Lateralization and motor stereotypy of song production in the brown-headed cowbird.

Song production in adult brown-headed cowbirds (Molothrus ater ater) is lateralized, with a slight right syringeal dominance. The left side of the syrinx produces low-frequency (200-2000 Hz) notes within the introductory note clusters, while the right side produces the higher-frequency (1500-6000 Hz) introductory notes, the interphrase unit (10-12 kHz), and the final high-frequency whistle (5-13 kHz). Cross-correlation analyses reveal that individual cowbirds produce each of their four to seven song types with a distinct stereotyped motor pattern--as judged by the patterns of syringeal airflow and subsyringeal pressure. The acoustic differences across song types are reflected in the differences in the bronchial airflow and air sac pressure patterns associated with song production. These motor differences are particularly striking within the second and third introductory note clusters where there is a rapid switching back and forth between the two sides of the syrinx in the production of notes. These motor skills may be especially important in producing behaviorally effective song.