Sorry, I loved the orchard mason bees on Whidbey Island when I lived there so I was expressing my enthusiasm. This site is all about bumblebees in Brooklyn. Here is what it says about where they nest:
“Often, it isn’t a lack of flowers that limits native bees but rather real estate. This isn’t a problem in my mostly wild garden, but the manicured turf and flowerbeds of suburbia offer few suitable nesting sites for social bees like bumblebees. Old mouse nests or rodent burrows are the preferred abodes, but bumblebee hives have also been found in deserted bird nests, rubbish piles, and thick, cushioned clumps of moss. If there are no abandoned bird nests or rubbish piles in your yard, you can buy a prefabricated bumblebee nest box. One example is the Humble Bumble Home, offered by a Washington-based, family-owned business called Knox Cellars (http://www.knoxcellars.com). It consists of a pine box, soft cotton nesting material, an instruction book on the life history of the bumblebee, and a clear plastic “ceiling” that allows you to lift the box’s wooden roof and observe the busy bees at work. I haven’t tried one, but I hear that bumblebees do take up residence in such structures, whether pre-fab or homemade.”