Monkey see, monkey do. I've found that if you have one tame bird and you want to tame others, it can make things easier. Even if you don't have a tame bird, if you have at least one bird willing to take the step, it makes things easier.
I experimented with 5 adult, flighted budgies. None were really tame. Just fed them every day first thing in the morning before changing out their food dishes.
[ame="https://www.youtube.com/watch?v=fUx81WHTUwk"]1 Bird in hand Leads to Many - YouTube[/ame]
Which eventually led to feeding them out of their cage.
[ame="https://www.youtube.com/watch?v=AlSm4uFZzVU"]More Budgies!!!! - YouTube[/ame]
I thought that was the end of it, but then I had a cockatiel who was watching me, and well, she wanted to the same behavior... only it took me two weeks to realize what she wanted!
[ame="https://www.youtube.com/watch?v=q88bN30qOjo"]Sunshine in the Morning - YouTube[/ame]
And since I started feeding one cockatiel by hand, another one watched and wanted the same behavior
[ame="https://www.youtube.com/watch?v=R9w9w8nMRmw"]Hesitant Faye - YouTube[/ame]
And you can see how much her behavior changed over time
[ame="https://www.youtube.com/watch?v=rH9ZWxhCSAE"]Not So Hesitant Faye - YouTube[/ame]
And that resulted in feeding the other cockatiels by hand. Pistachio was the most skittish cockatiel, ex-breeder who wanted nothing to do with humans. He showed the biggest change in behavior.
[ame="https://www.youtube.com/watch?v=XjKmHswgiHs"]Cockatiel Feeding - April 24th - YouTube[/ame]
If I kept it up, I could have also worked with gaining the trust of a wild caught african ringneck. Would prefer to find her an aviary situation with others of her kind, though..