We had our bird box taken over by Tree Bumblebees this year. They seem to keep themselves to themselves, pretty quiet tenants, have only had a moan when I hit the post holding the bird box with the lawn mower.
Bumblebees are lovely! I’ve picked up quite a few that have fallen onto paths, or got indoors and couldn’t find their way out. Just letting them climb onto my hand and put them somewhere safe, like some flowers, or let them fly away. I’ve got two bird boxes at the bottom of the garden, which the birds don’t seem to be bothered with, it would be nice if bumblebees took it on.