It is their method of stretching. This is also a way for a budgie to get some exercise.
Cage size really matters for these birds. After all, they need enough room to live comfortably and also flap their wings.
A variety of perches will give them a reason to fly, jump back and forth for fun, and of course stretch his wings as a means of staying active.
Your budgie can have fun with a play gym. Play gyms give your budgie the chance to climb, chew and ring bells. A ball is also a fun and simple toy for a budgie.