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The Suthers Laboratory

Animated Films of Song Production in Songbirds

The following QuickTime movies illustrate the different way in which Northern Cardinals (Cardinalis cardinalis) and Brown-headed Cowbirds (Molothrus ater ater) use their bipartite syrinx to produce their distinctive species-specific songs.

You may obtain permission to download these movies for non-commercial use in instructional settings such as classrooms or lectures at no cost, by sending an email request to Rod Suthers suthers(at) The accompanying wav files are in stereo so right and left side of the syrinx are heard on the corresponding speakers.

View Northern Cardinal Vocal Production Movie:

Click on either of links below picture to play video.

Play as WMV file    Play as SWF file

The songs of Northern Cardinals often include frequency modulated notes or syllables that sweep through a wide range of frequencies. Cardinals sing fundamental frequencies below about 3.5 kHz with the left side of their syrinx and higher frequencies with the right side. Continuous broad-band frequency sweeps are produced by switching sound production from one side to the other midway through the note. Most birds make this switch with such precise coordination that it is not detectable in the emitted vocalization. In this example, phonation switches from the right to left side of the syrinx during the downsweep. Upward sweeping notes are produced beginning on the left side and switching to the right.

View Brown-Headed Cowbird Vocal Production Movie:

Click on either of links below picture to play video.

Play as WMV file    Play as SWF file

The Brown-headed Cowbird uses a different pattern of syringeal lateralization. Cowbird songs contain 2 or 3 note clusters, each produced during a single breath. These are followed by a loud high pitched final whistle. Successive notes in each note cluster are produced on opposite sides of the syrinx, beginning with the left side for the first note. By alternating sides in this way the cowbird can adjust the silent side of the syrinx to start its note at a different pitch without a frequency slur between notes that follow each other without a silent interval between them. The final whistle is always sung on the right side.

The vocal organ or syrinx of Oscine songbirds is located at the junction between the primary bronchi and the trachea. Sound is generated by air flowing across a pair of fleshy tissue pads, the labia, present at the cranial end of each bronchus. The songbird syrinx thus contains two separate sound sources, one in each bronchus. Sound production in each bronchus is controlled independently by several muscles that are innervated by motor neurons in the tracheosyringeal branch of the hypoglossal nerve coming from the same side of the brain. During song, the labia on the side or sides of the syrinx that are producing sound are moved toward each other into the airflow through the bronchus, which is thought to generate Bernoulli forces causing them to vibrate and produce sound.

This bipartite syrinx with its two independent sound sources increases the diversity and acoustic complexity of bird song. Different species achieve different vocal effects by using the two sides of their syrinx in different ways. Some birds, such as grey catbirds and brown thrashers, can simultaneously produce different sounds on each side of the syrinx that are not harmonically related to each other. It is also possible to produce sound on only one side or to switch sound production from side to side by fully adducting the labia until they meet and close the bronchial lumen. This stops air from flowing through that side of the syrinx and silences it. Vocal diversity is increased by the fact that each side of the syrinx tends to be specialized in certain ways. The right side of the syrinx, for example, generally can produce a higher range of frequencies than can the left side.