Rob R. wrote:Just get rid of the cap entirely. No critters want to live in a chimney with coal smoke going through it...check it in the fall before you light up.
Well, small critters live in my chimney, STINK BUGS. I burn year round and when I shut down for annual cleaning, I was surprised when the fly ash I removed from chimney clean out and put in a bucket was moving. Thought it was a snake, but it was STINK BUGS, many dozens just wiggling away. Killed them by dumping the ash out and running over it with my tractor tire. I suspect they flew in from the top and stayed because it was warm. Some were dead but most were alive!