In the area of Queensland we're in these Cockatoo's are like pigeons, they're so plentiful that you see them flying in packs of 50 or more between gumtrees. This bloke and his pack of mates sit in a tree right over my car and love to ruin my paint:
http://en.wikipedia.org/wiki/Sulphur-crested_cockatoo#Pest_status Protected species, so you need a permit to shoot or poison them, they can do some serious damage especially in numbers and they're smart enough to create a considerable nuisance of themselves.
I'll bet you've already seen this a hundred times, but... from what I just googled it looks like you are pretty much doomed to fail. I could not find anything that mentioned pre-recorded bird-of-prey sounds, but I imagine if that worked you'd have heard of it, surely the idea is not original to me. However, if bb-guns are legal in Australia, which I doubt, you wouldn't have to shoot metal bb's from them. Paper wads or properly sized bits of soft clay might work and be less lethal. Maybe you could use a plastic fork in some way, if those are still legal. (*)(*)(*)(*)(*) stolen from the interwebs (*)(*)(*)(*)(*)(*) How to deter cockatoos Cockatoos are very intelligent and a well-planned strategic program needs to be set up to deter them. don't feed them - they will congregate where there is food and leave when the supply is gone, so check no one else nearby is feeding them make a scarecrow that looks like a bird of prey string fishing line over the area - this makes it hard for them to land paint any timber white - they do not like it give them a quick spray with a water bottle or hose hang netting over the affected area use taped alarm calls or a motion-activated alarm (providing it does not disturb your neighbours). Persist until the birds go - this may take more than a week.
http://hackaday.com/2012/03/20/bird...r-controlled-water-cannon-awesomeness-ensues/ (I'm a longtime hackaday member although it's lost a little of it's charm since the new owners took over a while back)
Not just in Queensland...shot this group on my last trip to Australia in Victoria... Not sure what's going on with the file - odd clicking noise on playback that's not there in the original, so maybe a problem with YouTube... Personally my favourite is the Galah...I know these birds are considered pests by many, but I just love them. They are such characters... We used to have a Goffin's cockatoo as a pet, so I think they are a lot of fun, although I understand they can be destructive. Cheers, Al
To paraphrase Mitch Hedberg, cutest infestation ever. Do you have OptiCoat in Australia? This is the sort of application that it's really made for.