Cockatoos, native to Australia, Indonesia, Moluccas, and Phillipines, have large and small varieties that range from 12 to 20 inches. Like cockatiels, they have crests that they can raise and lower. Cockatoos are also good mimics and demand a lot of attention. They would require a bird cage with bar spacing no smaller than 3/4"
The Marvelous Bird Cage that fit Cockatoos is the Bungalow Bird Cage: