You will be interested to know that this simple device was originally invented to scare seagulls and cormorants (shags) off boats, yachts and wharves. So successful, it was quickly tried in many other situations including Cockatoos.
In most situations these hawks will work provided the Cockatoos can see the Hawk profile above them from where they are landing. It must look like the Hawk is hovering high above the Cockatoos and the crop it is protecting. You must have the Hawk at least 6 metres in the air and preferably higher.
West Lindfield Bowling club were actually the first to use them for Cockies some 15 years ago. They used them to stop Cockatoos from destroying their bowling greens. The Hawks were so successful that they have now had them taken down for some time without any Cockies returning. Other bowling clubs to use Hawks are Denman, Shoalhaven Heads, Gresford, Beaudesert, Ballina and West Pennant Hills and North Ryde to mention just a few. Telstra are also using them throughout Western and Northern Victoria to stop Correllas and Cockatoos from damaging wiring, cables and instruments on their towers.
Many private individuals have successfully used hawks to stop Cockatoo damage around houses including TV and Solar Systems installed on roofs. Therefore in your situation they will work. Birds will always attack the edge of an olive grove. They start working from an outside row moving in row by row. Therefore by protecting the perimeter of the crop you can save the entire block. Cockatoos will usually come to a nearby tree adjacent to the block and the scout bird will fly in to taste the crop. It will then call the flock in while the scout bird flies back up into a tree to keep lookout for approaching danger. They like olive trees because they can sharpen and hone their beak on the soft timber. Their beaks never stop growing throughout their life and so need to be maintained by chewing softer wood.
All you need to do is to install the Hawks high above the areas where the birds are doing the damage. There is three methods. I have enclosed information on each method. In brief you can either spike the Hawk on the end of a 6 metre length of 25 mm pipe and stand the hawk and pipe up on the perimeter of crop. Plumbers plastic water pipe is very good as it comes in 6 metre lengths or galvanised pipe is also worth using.
Alternatively you can use strong fishing line or thin fencing wire to suspend the hawk between poles, trees or other high points around the crop so the Hawks are hovering above the area to be protected.
You will obtain excellent results using this method, saving you hundreds if not thousands of dollars in time and on loss of crop. The Hawk is unique because it is a full size imitation hawk made of durable weatherproof plastic. As birds instinctively fear the Hawk they are also scared to come within sight of the profile of this replica of a hovering Hawk.
Birds do not become used to the hawks presence. From previous customer experience in similar situations we can say that a Hawk Bird Scarer will work for you. If it doesn't, we offer you a money back guarantee.