One trait all cockatiels Nymphicus hollandicus have in common is a large, recurved crest which is erected during times of excitement or fear. Cockatiels share this trait with cockatoos and it has long been assumed that cockatiels must be biologically related to the cockatoo.
The males of the species have a bright yellow face with bold orange cheek patches. The females have similar characteristics, but their face plumage is duller and they have barring on the underside of the tail. There are several colour mutations available in today’s aviculture.