The bird seems a hybrid of Long-billed Corella X Little Corella. The long bill and red color on the throat is shown but not as obvious as Long-billed Corella. It is paired up with a Little Corella. They were guarding a hollow and did not leave. This bird kept preening the Little Corella and was bigger than the Little Corella.
Further advice is not able to be definite but your id is likely. As the number of Little Corella increase the probability of hybrids will presumably increase so we need to keep a sharp eye out for these hybrids. I will go with your id but always happy to change my mind! Chris