Hello. I am Dr Lachance and will be happy to answer your question tonight.
The best way to use Goldenseal is to treat your parrot for about 10 days by placing glycerin-based echinacea/goldenseal tincture into the drinking water (about twenty drops per 8 ounces) and use this as the sole water source. Please make sure at first that your parrot likes and drink the "tea" by using also a bowl of fresh water. When you determine that he is drinking both, then use the tea as the sole water source.
There is also another product that can boost his immune system and it is called "Garden of Life Primal Defense". It is a soil based probiotic supplement. Use Primal Defense sprinkled onto soft foods five days per week. That should help his digestive tract and make it stronger.
I hope that answers your question and that Rico will feel better soon. Make sure he drinks plenty of fluids!!