Answer by
nuttree (1596)
Cockatiels are the smallest birds in the cockatoo family, with a length of 12 to 13 inches, including a long set of tail feathers. Like other cockatoos, cockatiels have a crest on their heads, which can be vertical, oblique or flat, depending on the bird's emotional state. Cockatiels also have orange check patches -- bright for males, subdued for females.