Male and female Trumpeter Swans give the characteristic deep, trumpeting “oh-OH” call, with the second syllable emphasized. The call is softer and more nasal-sounding when made with the mouth closed. Trumpeter Swans call to keep the pair or family together, to defend territories, or to sound an alarm. Both sexes also use a flat-toned, single-syllable “hoo” call to locate each other. Younger swans make a higher-pitched call, and develop their adult tone by the time they’re 6-8 months old.
Trumpeter Swans slap the water aggressively with their large webbed feet when approaching an intruder. Their wings and feet also slap the water’s surface during takeoff.