So far, we haven't noticed any issues with birds or other critters. If we do, I'll add a screen, but I didn't want to risk making things easier for spiders, or helping water splash the holes if I didn't have to.
We did have carpenter ants climb up behind the sticks so I need to figure out our solution to that. I'm really hoping thats new and that they didn't get into the bee holes or take any eggs. The tree seems healthy so I'm thinking the bee house was what appealed to them?