Some folks have been talking about lice and mites, I have also used ivermectin pour-on, but am now using wood ashes for my birds to dust in. They seem to love dustbathing in the ashes and I haven't seen any lice or mites since I started providing it for them, I believe in doing things the easy way whenever possible, and as long as this is effective I'm all for letting the birds treat themselves. I don't have a woodstove but a quick post on craigslist got me a continuing source for all I'll ever need.
It needs to be pointed out that "Ivomec Eprinex" is NOT ivermectin. Same class but not exactly the same drug. And there is a big difference, in my opinion (and that of the Canadian regulators apparently because I can buy Ivomec's ivermectin from the feed store but I have to get Eprinex from the vet.)