OK, well, you need to have someone find the nest, and get rid of it; and you will have to make sure there are no other places other than the vent where they can get in, and close those up.
I am here as well; I have merely been keeping a low profile. Wishing you well with your diagnosis @Charlet. Knowing for certain what it is that ails you is the first step toward effective management of it.
Really, @Lucy?!?! I could ask that or start asking myself, 'Where in The World is Lee Jordan?' or 'Where in The World are Zack and Ivy?' I mean no one knows where everybody us at.