I've heard of the human benefits of turmeric and knew about garlic properties for any creatures for years...HUGE garlic fan here. But am going to give it a shot for the birds as well. I have a garlic press, so it can be freshly crushed...and will get a big container of turmeric today. But the rosemary that someone previously mentioned...not sure I will be able to get that in sufficient volume regularly to treat 100+ birds. But the garlic and turmeric is definitely a start.
Thanks all!
Buy plants if you can, I suggest, rosemary isn't hard to grow once you know how. I knew one guy who propagated thousands by hand, he just stuck sprigs in soil and misted them. They don't like non misted water while shooting from sprigs, apparently. I'm quite a fledgeling gardener myself but I've still managed to grow large bushes of rosemary.
If you live in an area too cold for it, you could try a variety of greenhouse or warmhouse growing techniques, there's a lot of suggestions out there that people have been using in cold climes.
Also, if you look for bulk sellers you can get a lot of rosemary and other herbs pretty cheaply... Comparatively anyway, considering what they sell the tiny satchels for LOL!
Best wishes.