Black Shoulderd Kite
it is an juvenile ELANUS Kite, two species occur in Australia: Australian Black-Shouldered Kite Elanus axillaris and Letter-winged Kite Elanus scriptus. Adults are grey, white and black but juveniles much more browner. It is very difficult to differentiate sitting juveniles, you should check the underwing when flying, with a dark bar on greater flight covers in Letter-winged. In that area it is most probably Black-shouldered Kite.
nice picture anyway