Male Trumpeter Hornbills swallow mud and turn it into little balls that they regurgitate to females to help them seal the openings of their nests. Females remain in the nest all through incubation and for several weeks after the eggs have hatched, relying solely on the male for food.
 
The very loud cries of male Trumpeter Hornbills sound like a baby’s wails. Their casques are much larger than the females’. They function mainly as a soundbox, amplifying the vibrations of the vocal chords, similarly to the sound inside violins.
 
Male hornbills swallow several fruits and carry them in their oesophagus then regurgitate them into their beak one by one to give them to the females and to the young inside the nest.