kanti

Kanti works both ways: intransitive when birds do it, transitive when you sing an actual song. The root hands you kanto for the song itself, kantisto for a singer by trade, and kantado for singing as an ongoing activity, which is the distinction -ad- exists to make. Esperanto culture leans on this word more than most languages do, since every congress opens by singing La Espero, the movement's anthem, and knowing what the verb means beats mouthing along.