Song syntax changes in Bengalese finches singing in a helium atmosphere.

Male Bengalese finches rely heavily on hearing to maintain adult songs and deafening a bird changes its song syntax immediately. Eight adult male Bengalese finches were placed in a helium atmosphere, which changes the resonance of the vocal tract. Undirected songs were recorded before, during and after this procedure, and the changes in song structure were analyzed. A helium environment increases the amplitude of higher harmonics, as in other bird species. Furthermore, note-to-note transition patterns that were never recorded when singing in normal air appeared in the songs sung in helium air. Therefore, helium can be used to cause reversible syntactical re-organization of songs in Bengalese finches, which can be used to study the neural mechanisms of auditory feedback.