Cockatoos: Louder Than All The Rest

The cockatoo is the loudest of all the parrots. 

Picture From Oakland Zoo

Their loudness comes from a history of having to communicate long distances with one another in dark, thick forests. Their vocalizations serve a number of functions, including allowing individuals to recognize one another, alerting others of predators, indicating individual moods, maintaining the cohesion of a flock and as warnings when defending nests