What should I do if I find a swarm of bees? - Pollinators & Pollination (msu.edu)

Is the swarm loosely clustered on the outside of the chimney? Or is the swarm inside the chimney? Normally a swarm hangs in an exposed area close to the hive and then moves into a cavity to establish a hive. If the swarm moved inside, then I'd assume that they are establishing their hive and building comb in the chimney. 

If the swarm is exposed and clustered on the outside of the chimney, then chances are they will move on to cavity within a few hours to a few days. You may or may not have luck luring them into a hive box or swarm trap.

If the colony is establishing a hive in the chimney, it is unlikely to leave on its own. You can hire someone from Michigan Beekeepers Association's cutout list for help removing them: Michigan Beekeepers Association - Cutout List (michiganbees.org).



No problem! I realized my comment on absconding was based on honey bee behavior and not fire safety. Please consult with a fire safety expert before using the fireplace if the chimney is fully or partly obstructed.