Male gang-gang cockatoo seen from a distance chewing around hollow. No longer visible in these photos. Did hear gang-gang calls, not clear if was the male or if there was another nearby. The large amount of debris at the base of the tree, along with a relatively freshly snapped branch, suggest there has been some serious excavating to build the hollow.
Thanks Lisa - It is in the vicinity of where Gang-gangs have nested before - the chip looks more like the work of Sulphur Crested Cockatoos who tend to evacuate strips of wood as opposed to Gang-gangs who excavate more chunky bits so perhaps both species have interest in this hollow - but would be interested if you do catch Gang-gangs excavating strips.