cockatiel, Crested, small, gray Australian parrot (Nymphicus hollandicus). It has a yellow head, red ear patches, and a heavy beak used to crack nuts. The cockatiel is in the same family (Cacatuidae) as the larger cockatoo. About 13 in. (32 cm) long, the cockatiel lives in open areas and eats grass seeds. One of the most common pet parrots, it is bred in many colour variations.