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Abstract
The white-crowned sparrow (Zonotrichia leucophrys ) is a songbird that has long served as a preferred model system for the study of song learning. Of particular interest has been the role that syntactical (phrase order) and phonological (phrase structure) cues play in guiding song memorization and ontogeny. In the present study, we manipulated song syntax information in tape-tutored white-crowned sparrows to explore the minimum information requirements necessary for the normal development of syntactical and phonological parameters of song. Groups of birds were tutored with one of the following: (1) no song (acoustic isolation) (2) isolated phrases, (3) phrase pairs, in either a natural or reverse order, or (4) full song, in either a natural or reverse order.
We found that phrase-pair information is the minimal syntax information necessary for complete song assembly. Birds tutored with phrase pairs assemble complete song, while those tutored with isolated phrases do not. Although this is the case, we found that white-crowned sparrows tutored with more complete syntax information (i.e., full song) exhibited syntactical differences in their crystallized songs relative to birds tutored with phrase pairs, suggesting that this additional information is stored in the songbird brain and later accessed. We also observed that sparrows tutored with phonology, but not syntax information crystallized songs with deficient phonology relative to birds tutored with both syntax and phonology information.
We examined trajectories of syntax development in all groups to determine whether the ontogeny of acoustic features also differs among groups. We found that specific elements of syntax development could be altered by tutor syntax information, while other aspects of syntax development appeared to be guided by innate factors.
We also examined trajectories of phonology development in all groups. We found that birds produced phrases having only moderate similarity to tutors for much of developmental time. Late in development, all birds showed significant improvements in phrase phonology that corresponded in time to improvements in syntactical parameters. We also observed that syntax and phonology trajectories for individual birds were tightly linked in time. This finding provides further evidence that phrase phonology and song syntax are linked in the songbird brain.