Little Corella
Cacatua sanguinea
The little corella is a small white cockatoo growing to 35–41 cm (14–16 in) in length and weighs 370–630 g (13–22 oz), with a mean weight of 525 g (1.157 lb). It is similar in appearance to both the long-billed corella and the western corella, but the little corella is smaller, and unlike either of those species, it has upper and lower mandibles of similar length. It is easily distinguished from the long-billed corella by the lack of an orange throat bar. C. s. normantoni and C. s. transfreta are a little smaller than the nominate form. C. s. Voice: The call consists of high pitched notes and screeches somewhat similar to the sulphur-crested cockatoo. Large flocks will call simultaneously and can create a deafening screeching sound audible from several kilometers away.
ID text from Wikipedia, CC BY-SA 4.0

Long-billed Corella
Cacatua tenuirostris
The adult long-billed corella measures from 38 to 41 cm in length, has a wingspan around 80–90 cm, and averages 567 g in weight. It has a long, bone-coloured beak, and a rim of featherless, bluish skin around the eyes. The plumage is predominantly white with reddish feathers around the eyes and lores. The underside of the wings and tail feathers are tinged with yellow. Voice: The call of the long-billed corella is a quick, quavering, falsetto currup!, wulluk-wulluk, or cadillac-cadillac combined with harsh screeches.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Little Corella and Long-billed Corella.