Juvenile Australian Koel (possibly Eudynamys cyanocephalus). A large cuckoo. Juveniles and females have colouring similar to this, but the adult males are blue-black.
Migratory bird which lives in the tropics, but migrates south during the (Southern Hemisphere) summer to breed. It is a brood parasite. In Australia, their hosts are mainly large honeyeaters (especially Noisy Friarbirds and Red Wattlebirds). The young do not attempt to kill the host chicks.
This individual was found at an almost featherless chick and was hand-raised. This picture was taken after it was "soft" released. It was supported through to March when it left for the migration north. In summer, the adults Koels are known for their constant (and slightly annoying) "oooahooo" sound from before dawn.