Hole behind gutter, worried about creatures

That's the weirdest title I've ever written for anything ever.

Basically, I noticed in the spring that there was some bird nesting type activity going on around the gutter on the second storey. I went up on the roof not long after and noticed that one of the boards that the gutter is attached to had come loose. Presumably the birds had nested in there (I know I would have). My question now is, is it safe to go and repair/replace the board? How can I be sure? What if some other critter has moved in?

I suppose this is more of a "nature" question than a "gutter" question, but I wasn't sure where else to put it.

Cheerios,
Marc

 

Set some kind of a flimsy barrier over the hole so you can tell if anything goes through - if undisturbed after a couple days, cover the hole and move on to the next project

 

Thanks Mitch. Is there a time of day to do this when there's the least likelyhood of me getting rabies and/or falling off the ladder because I hear a strange noise?

 

That would depend on what's in there, if anything

I'd go daytime for visibility and just plan to be quick