A mouse got inside my city hive because I waited too long to put on mouse-proofing mesh.
From what I can tell, the mouse (or mice) was in the hive for a long time and scared the bees, queen and all, into a honey super that I had placed above the inner cover during a late fall feeding.
For an entire colony to abandon the brood nest by squeezing through an inner cover hole to cluster inside a honey super — that’s not normal.
I should have put my mouse-proofing mesh on as soon as I knew I wouldn’t need to move the bottom box for the rest of the year.
UPDATE: I use 6mm mesh to keep both shrews and mice out now.
This year I did keep the mouse mesh on all summer. It didn’t bother the bees and I know I don’t have a mouse in there. After losing mine last year from mice it cost a lot to replace them
Yup, that’s my thinking too. Except for maybe cleaning the bottom boards after winter, unless I’m moving a hive to a new location, I see not reason why I can’t keep the mesh on all year. It doesn’t knock the pollen off the bees’ legs. It doesn’t block ventilation. It does nothing to get in the way at all, as far as I see.
Sorry to hear this. Some beekeepers do say that the mouse guard can knock pollen off the bees legs and also slow the foragers returning during a nectar flow. But considering how much damage a mouse can wreak these are fairly small cons.