After my two adoptive welchies mostly just sat around in the cage and lacked many budgie-typical behaviors (curiosity, nibbling, desire to fly, etc.), I was soon looking for a solution.
After some consideration, I then decided that these needed a role model for normal budgie behavior and got two “normal” young birds from a trustworthy breeder.

So the two budgies, then but four pieces and I now have a little flock. Even though it was not originally planned this way, I have to say that my two adopted budgies have become much livelier and have already picked up one or two budgie-typical behaviors.
And here he is now my little crush. All four budgies together on the climbing playground during free flight.