Amino acids and the proteins constructed from them are needed for feather, bone, hormone, muscle, and enzyme production. Protein can also be used as a source of energy.
To maximize the body and feather growth of exhibition budgerigars I find they need a good mix of both vegetable and animal protein.
Mealworms are an excellent source of animal protein that are easy to produce in the quantities needed to supply your birds on a regular basis.
Budgerigars love Mealworms once they get the taste... especially live ones.
I feed home-grown live mealworms in the flight and stock cages, and freeze-dried mealworms in the breeding cages.
If you do not like the idea of growing your own you will find freeze-dried mealworms at most feed stores catering to wild bird enthusiasts or finch breeders.
Just soak the dried mealworms in warm water for 5-10 minutes till they plump up and they are ready to feed.
Mealworms are easy to grow. I bought 1,000 over 3 years ago and the "colony" is still providing plenty of mealworms treats that are fed 2-3 times each week.
Our "colony" breeds in a plastic tub. All you need is supply of wheat or oat bran and vegetable scraps to feed every second day. Mine get sliced cucumber, broccoli stalks, cauliflower stalks, apple, and any other fruit or veges that have "moist" flesh.
When time to feed separate the live mealworms and put them in fresh oat bran for 24 hours to help clean their digestive track.
I feed the live mealworms in a deep sided dish in the flights so there is no chance they can climb out...
Be aware that mealworms have a life cycle. From worms they pupate then turn into beetles which in turn lay eggs and eventually die.
After the beetles die the colony will appear dormant until the eggs start to hatch. Don't make the mistake of throwing out the powdery residue and the bottom of the tub... You will be throwing out thousands of eggs that are waiting to hatch.
