I have seen some birds that learn to perch before they fledge, and before they fly, even. I was raising a dove that didn't fly before she learned how to perch. I've also seen parrotlet babies, who's feathers were just starting to come in, that managed to climb to a perch in the cage it was sharing with it's parents and siblings.

If you work with a bird before it leaves the nest it can start learning how it's done, but it's not going to become highly skilled at it until it reaches the natural developmental age for it. I'll put my almost-fledged babies on my finger for a little perch practice so they won't be as utterly incompetent at sitting on a perch when they leave the nest, but they'll still have significant problems at first trying to sit on a perch without falling off.

The capability probably varies by species. With a lot of birds that have an open nest in a tree, the babies will engage in "branching" behavior before they fledge, where they start sitting on the branch next to the nest. But parrots don't do this since they're cavity nesters. They'll start sitting in the nest entrance for a few days before they fledge, but they usually don't have the scope to actually sit on a branch.

When i was there last week she said they would soon be learning how to perch n she was putting them in a cage. By time i get him, he will know how to perch and be able to go in the cage i got.