You may think it is harmless but cockatoos are extremely destructive. You may not have any timber on your block of units, but what about the numerous other buildings in the area? If they end up with tens of thousands of dollars of damage, as is often the case, are you going to offer to foot the bill?
Secondly as for which by-law you breach, you breach By-Law 1. No good saying they fly past screeching anyway. You are encouraging them to the area. Once again if it is no you that they are bothering then it will be hundreds of other home owners in your area.
Claiming that you are not making the noise (the cockatoos are) is like having your radio turned up full and claiming it is the radio making the noise, not you. Claiming they make a noise anyway is like saying people drive past with their radios blaring. Bottom line is your actions are adding to the problem.
The other problem is their droppings. I presume you do not volunteer to clean up any that fall onto common property or other people’s balconies.
If you want the freedom to feed wild birds (in breach of the recommendations of all wildlife experts), go out in the bush and live on a farm.