escapees? (cacatua tenuirostris)

Well they are having the time of their live, well done

Yes, according to my book, they're well out of their range there. Lately a lot of Australian birds have been turning up in unusual places, probably because of the drought, but whether these birds would make it across the Nullarbor is a moot point - so they are probably escapees. They look very happy with what you've provided. :-O