The cockatiel, is a medium-sized parrot that is a member of its own branch of the cockatoo family endemic to Australia. They are prized as household pets and companion parrots throughout the world. The cockatiel's distinctive crest expresses the animal's emotional state. The crest is dramatically vertical when the cockatiel is startled or excited, gently oblique in its neutral or relaxed state, and flattened close to the head when the animal is angry or defensive.