I have a colony of bees that always clusters on the west side of their hive — and I don’t know why.
I’ve had this colony for almost four years now (she’s an old queen that I started from a swarm cell) and I’ve noticed this clustering behaviour since day one. Even when I rearrange the frames of the brood nest in the spring so all the brood is in the middle of the hive, the brood nest eventually shifts to the west side of the hive.
I’ve checked everything over the years and there’s nothing unusual about the hive set up. No signs of mice, no leaks on one side of the hive, nothing. I’ve used various hive bodies and other hive components. I even moved the hive to a different beeyard and rotated it so the cluster was on the east side. Within a month the cluster shifted to the west side. My best guess is the bees prefer the heat of the setting sun.