Six cygnet calls, eight adult calls, and one nonvocal sound of Trumpeter Swans are categorized and described. Calls vary greatly in complexity. Many form graded series, while others are discrete. Most of the cygnet calls are involved with soliciting aid from a parent, while adult calls have a wider variety of functions.
Patton-Gross, M. and M.S. Ficken. 1992. Acoustic communication of the trumpeter swan (Cygnus buccinator). Field Station Bulletin 25(1): 14-37.