This is what we found on Wikipedia regarding the Corella:

Licmetis is a subgenus of the white cockatoos (genus Cacatua). They are collectively known as corellas in Australia. Three of the six species are primarily – or only – found in Australia, while the Philippines, Indonesia, and the Solomons each have an endemic species. They are relatively small cockatoos and – unlike the members of the subgenus Cacatua – all have pale bills. While most show yellow-tinged underwings and some red to the face, none has conspicuously coloured crests.