Cockatoo's are very destructive to timber in an aviary something that had not experienced until I got my pair of Galah's.
It started with structural wood, shelves, perches, nesting boxes and feeding containers. Some of my other species chew a little but nothing to the degree of my Galah's.
I now combat it by keeping a lot of branches in the aviary giving them plenty of fodder to chew on. I put a large paper bark branch in and they chewed all the bark from the branch in a day.
I also thought being nearly twice the size of my next largest bird they would have a greater appetite but they eat little more than my Green cheeked Conure or Indian Ringnecks even though I provide them with more food.