Sorry to hear, Glen. I had to battle with crows earlier this season and dealing with problem birds is difficult when you want to keep the good ones around!
I made these fancy (
) bird-scarers to put in the garden. They clank like mad when there's a breeze, and the crows hate them. The hummingbirds have been oblivious to them though, which I am thankful for. I drew a face on it with a paint pen so if there was no wind they had an angry 'face' staring at them
They have not been back since I put these up.
I don't know if it would work for cockatoos, but it didn't cost much to make them, nor did it take much time...might be worth a try.
Hope the damage isn't too horrible.