Quackingly

...expressing their satisfaction in deep, megaphone voices, until they are quite sure we have heard, when they go quackingly away to the nearest pond.

His anger broke and he cursed quackingly, cursed in bleats, cursed until he drooled and had to apply his sleeve to his mouth.

...some smartly styled but quackingly played overtures by the Monte Carlo Operators under Louis Frémaux...