Likely a Long-billed/Little Corella breeding pair. Pair was following each other around, some pair bonding activity (allopreening). Long-billed was investigating a hollow in the tree. Looks like this pair may have been reported previously (see sighting 4245789).
Was a sulphur-crested cockatoo nest in the same tree.
Have seen the pair the past two mornings that I've been at Red Hill.