If I may, not toxic does not make it good. Food with little nutrional value only take up the space of nutritious foods.
If you take a 100 grams of popcorn, nothing added, bare plain popcorn, and put it in the microwave, all you get is
27 IU of vitamine A, carrots for example have 16700 IU dandilion even more.
No B, E and D vitamines
10 Mg of calcium completely oblitared by a whooping 300 mg of phosphorus, I don't know if you know about the calcium phosphorous ratio, but this phosphorus cancels all calcium.
Sesame seeds for example have 975 mg of calcium ans 639 phosphorus. Almost two to one, the perfect ratio for a parrot. When germinated, the fat is reduce considerably and fat is necessary to the métabolism of fat soluble vitamines.
There are other benifits. The same 100 grams of sesame seeds will have lysine (580 mg) and méthionnine (570 mg) respectively while your popcorn has lysine (338 mg) and méthionnine (252 mg).
Popcorn has no choline. Sesame seeds have 25.6 mg of choline per 100 gr. Other food have choline too, green peas, spinach, broccoli.
In sesame seeds the carbs amount to 23gr and the fibers 12 gr almost the same as your pop corn. Your popcorn has 78 grams of carbohydrates of which only 15mg is fiber, the rest is starch to make your budgie fat and possibly contribute to fatty tumors has he ages.
These are some of the nutrients your budgies need most.
If you give them popcorn, don't forget their relative size and do not spoil their dinner.
Treats are human concepts. Animal need nutritious food for good health. If you raise them to appreciate nutritious food as treats, then there is a benefit to it. When you give treats, you are treating yourself at the expense of their optimal health. Birds are too fragile for treats.
Also, there is a lot of corn in most pellets, they do not need more corn, it is just bloody filler. I know I sound like a bore, but I really mean well. Martine.