Possible Functions
Because the lateralized control of songs of certain species, such as cardinals, demands such precision in motor control, the ability to produce high-quality, seamless syllables may provide an indicator of fitness to potential mates. Supporting this hypothesis, certain syllables called "sexy syllables" sung by male canaries at high frequency are more effective than others in eliciting sexual displays from females. These particular syllables all contain two notes that are sung alternately by each side of the syrinx. Thus, control of the rapid switching from one side of the syrinx to the other is required to produce these attractive syllables.
Lateralization also allows for rapid and abrupt frequency changes. Studies of mockingbirds mimicking tone pairs in which the first tone was either higher or lower than a median tone of 2 kHz (either side is capable of producing this median tone) revealed that alternating sides of the syrinx for each note was necessary to reproduce them correctly. Correct mimicking was performed by singing the first syllable with the appropriate side of the syrinx—right for a high frequency tone and left for low frequency—and the second median tone with the opposite side. When the same side was used for both tones, the step-wise frequency change between the tones became slurred, suggesting that lateralization allows for abrupt frequency changes in song.
Read more about this topic: Lateralization Of Bird Song
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