I have the exact same issue with Myna birds and had put out a rubber snake to scare them away, which worked for about 2 days. One day while I was rotating my rubber snakes there was a massive wedge tailed eagle perching in a tree watching the birds. I had a heart attack as I have a small dog outside who does a good job at scaring away the birds who attack but I knew this bird could kill her easily. When it saw me it freaked out, swopped down and took my rubber snake!!!! I don't put them out anymore because I don't want him to come out incase. Pretty amazing though! I have lined my aviary with breathable fly netting which you can get for a pretty good price at bunnings; It is made of tiny wires so it takes a while for a Myner bird to peck it's way through and by the time it tries to do that my lovely dog would have scared it away. I totally recommend doing this as one of my budgies was grabbed and died after a heart attack :( since doing this I haven't had any issues like that with the birds, except for when they pretend to swoop which gives them a little scare, once again nothing serious and they eventually get used to.
Hope this was helpful :)