A Comparison Between Development of Bird Song and Development of Other Displays

The ontogeny of bird song is compared with that of other vocal and postural displays. At the level of description both types of display show a gradual development towards a more conspicuous and stereotyped form. In addition, the developmental outcome shows in both cases plasticity under the influence of social experience. At the level of mechanisms similarities and differences are discussed. Although song development has been studied mainly from the perspective of learning, and development of other displays from the perspective of motivational changes, both these mechanisms play a role in the development of both types of display. The development of both types may be influenced by the reactions of conspecifics to the display performed and sex hormones. The latter may enhance the expression of species specific properties and influence crystallization or form fixation in both song and other displays. Imitation, so important for normal song development in many song bird species, does not seem to influence the development of postural displays, but there is some preliminary evidence that it may influence the development of vocal display other than song. The influence of sensory-motor learning (motor matching) is discussed.