Actually it also matters what type of worm you're dealing with...for whatever reason I'm just assuming that you're seeing roundworms.
If you're seeing tapeworms this product will not work.
Did you get any pictures of the worms?
You can buy that one that is sold for goats or you can buy the horse paste.
It really depends on how many birds you have to treat on which one you should buy.
There is no such thing as a natural dewormer.
If you want to get rid of the worms before they harm your birds then buy a real dewormer.
Also if you're actually seeing worms in their poop then your birds have a heavy worm load.