Cacatua sanguinea or the Little Corella.
My bird identification skills sometimes leave a bit to be desired, and the process typically involves me taking photos of birds adn afterwards trying to work out what the actual bird was. This is one of those cases where during a visit to the lake at Lakeside Pakenham we saw (and fed) these birds.
After a bit of looking, I believe them to be Corella’s which is a subgenus of Cockatoo’s. The beak does not look long enough to be a long beaked Corella so i suspect it is more likely to be a little corella which is Cacatua sanguinea, if I have the ID wrong please yell out and I will correct it :).
Taken with Nikon D5300, and Tamron 150-600mm