Actually it's called fledging when they leave the nest. They start learning to feed themselves when they fledge, because they don't have any opportunity to do it while they're in the nest - the only food in there is what mom and dad regurgitate to them. It takes about a month for them to get skillful enough to meet all their needs by feeding themselves, and when that happens they are weaned.
I made a screen door for the bird room. It has detachable hinges so I can easily take it completely out of the door frame when I want to, and I can also latch it to keep all those pesky cockatiels inside.
