How birds memorise and retrieve information encoded on different hierarchy levels of singing

The singing of birds is a learned behavior with a hierarchical structure that resembles some structural properties of human language. The interactionally most significant hierarchy level is given by songs which formally are comparable to human sentences. We studied how exposure to serial learning tasks would affect the structure of both sequences of songs and sequences of elements composing such songs. Analyses of singing performed by tutored Nightingales (n=24) revealed two results: Imitations of element sequences reflected a kind of 'gestalt'-learning related to a centered song 'nucleus' where the phonology and syntax of elements appeared stereotyped. Imitations of song sequences, however, reflected a kind of 'list'-learning that was linked to formations of plastic song clusters and a serially flexible retrieval of songs. These findings contrast to language properties, e.g. by suggesting that the freedom of unit combination is high at the level of song sequences, but decreases in top-down direction.