Now, the only way for pet birds to get enough vit D3 is through supplements because unless the bird is exposed to direct sunlight every day (we don't know how long this exposure needs to be for parrots but, for people, is a minimum of 20 minutes a day), there is no plant food (the ONLY thing that companion parrots should consume) that provides it BUT one needs to be careful because too much is as bad as too little.
https://www.mnn.com/health/fitness-well ... e-40378997