The need for empty tree hollows. We have often seen and heard cockatoos screech and spread their wings at trees. They are aware of the possums that sleep during the day inside the hollows of older trees and are trying to disturb them. The problem is these hollows are needed for nests as well as sleeping quarters and there are fewer of them available due to deforestation. So what can you do? Add a nest box or hollow log to your backyard and see what pops out for a apple. This is our backyard possum in the box that Steve built and we knew she was there because the Noisy Miners told us! This is especially important with the Swift Parrot that it is on the endangered list due to Sugar gliders needing tree hollows as well and yes boxes are being put up in Nature Parks for this very reason.