Since I've started providing Digby with a box, a hideaway of some sort I've noticed that his behavior improved a lot and he behaves a lot more hormonal and destructive when he doesn't have a box to hide in.
In fact, this is how I found out that he loves to have a box to hide in: he used to try and get in every dark nook and cranny when he just moved in with us. That was of course a sign of hormonal behavior as I thought and I tried to discourage it as much as I could but nothing helped. Tirelessly he would seek the corners, chew the walls and sometimes even go to sleep under the sofa! Until I found the solution - I gave him a box, he loved it, he calmed down and he has been happy ever since.
His hideaways are not always boxes, sometimes they are baskets or even a paper bag (given only under supervision). I never place them in his cage as he just doesn't seem to be interested or brave enough to go in them when in the cage. They always rest on his part of the windowsill.
It works for Digby, but I am safe in knowledge that he is a boy and not going to lay an egg. I would not advise giving boxes to female parrots. Egg laying is a dangerous thing and can deplete the bird's calcium storage and cause egg binding.
These are just some of the hideaways he had over the year:
I enjoy providing Digby, and Dudley the rabbit too, with large boxes. I usually put something inside as well, like a phone book or old toys for shredding. Then I watch them work, chew, shred, shaping their own habitat. They make the doors where they want them to be, Digby shreds the paper and toys to create perfect soft, finely shredded base of the box. With having a box he has something to work on, daily. Once I see there is nothing left to work on and the box is starting to look old and sad I throw it away and replace with a new clean one.
This is not strictly a hideaway but a pine shelf of his, but it does provide some sort of shelter and he enjoyed sitting on it, shaping it up, moving things around, trimming the wood.