BIRD SONG
One instance in the animal kingdom with parallels to human music is bird song. Much has recently been discovered about the development of song in birds. Some species are restricted to a single song learned by all individuals, while other species have a range of songs and dialects, depending on environmental stimulation. The most important auditory stimuli for birds are the sounds of other birds, including family or flock members and territorial rivals. For all bird species, there is a prescribed path to development of the final song, beginning with the subsong, passing through plastic song, until the bird achieves the species song or songs. This process is similar to the steps through which young children pass as they first babble and then mimic pieces of the songs they hear around them, although the ultimate output of human singers is much vaster and more varied than even the most impressive bird repertoire.
Underlying all avian vocal activity is the syrinx, an organ unique to birds that is located at the first major branching of the windpipe and is linked to the brain. There are general parallels between the syrinx in birds and the larynx in humans. Both produce sound when air is forced through the windpipe, causing thin membranes to vibrate. However, compared to the human larynx, which uses only about two percent of exhaled air, the syrinx is a far more efficient sound-producing mechanism that can create sound from nearly all the air passing through it.
Possibly the most interesting aspect of bird song from the perspective of human intelligence is its foundation in the central nervous system. Like humans, birds have large brains relative to their body size. Song is a complex activity that young birds must learn, and learning implies that higher-brain activity must be complex in the control of song. This control is associated with two song-control centers in the avian brain. If the links between these centers and the syrinx are interrupted, a bird is unable to produce normal song. Moreover, bird song is one of the few instances in the animal kingdom of a skill that is lateralized; the song- control centers are located in the left side of the avian brain. A lesion there will destroy bird song, while a similar lesion in the right half of the brain will result in much less damage.
Glossary:
- repertoire: stock of songs
- avian: relating to birds
- windpipe: main airway to the lungs; trachea