Memorization and reproduction of songs in nightingales (Luscinia megarhynchos): evidence for package formation

Summary

To examine the properties of avian song memorization, handraised nightingales (Lusdnia megarhynchos) were exposed to three strings composed of 21 or 12 different song types (Fig. 1) which they heard only during the tutoring programs. The analysis of the birds' singing performed several months later revealed a kind of song memorization and production which, hitherto, had not been studied in song birds and is called ‘package formation.’

Each package was a temporally consistent group of acquired song types which could be traced back to a coherent succession of, usually, three to five (max. seven) model song types. Model song types which a bird failed to acquire were located outside those sequences of model song types that had been acquired and later formed the packages. In contrast to the order of the tutored strings, packages were sung in a variable order. In parallel, neither the frequency of occurrence of the packages nor the performance length was related to the size of the package.

We infer from these results that package formation reflects basic properties of the nightingales' song-type memories, which — through segmentation of serially presented learning stimuli — may facilitate the acquisition of large signal repertoires.