The role of hierarchy levels in vocal imitations of songbirds

The singing of adult birds shows a clear hierarchical organization and, due to its development through vocal imitation of sound patterns. makes an exc ellent biological model to examine the variables that influence the imitati on of patterns on different hierarchy levels, e.g., songs and elements comp osing the songs. We studied such variables in the nightingale (Luscinia meg arhynchos), i.e., a species that in the wild uses a large repertoire of son gs. Subjects were raised in the lab and tutored by presenting them with a s erial learning task, here a sequence of differently patterned songs. Analys es of singing, which the trained subjects performed at the end of their voc al ontogeny, allowed us to uncover hierarchy-related accomplishments and al so specific constraints in learning by imitation. Our results showed that a n imitation of elements and element sequences reflected a kind of "gestalt" learning, which finally became visible in the form of specific song patter ns. An imitation of song sequences, on the other hand, reflected a kind of "list" learning, which finally emerged into the formation of specific subre pertoires of song types. The structure of such subrepertoires mirrored the serial order of imitated songs but allowed, nevertheless, a serially flexib le retrieval of single types of songs. These findings contribute to a bette r understanding of relationships between signal imitation and signal use du ring vocal interactions among songbirds.