I have an owl house I removed for a customer this summer that I never got around to taking the bees out of. It was a large house with about six combs drawn on the outside.
I'm not sure if it had swarmed or just dwindling, but it has been getting smaller lately. Tuesday afternoon I witnessed what looked like a swarm issue from it. I watched as it circled over the apiary and settled on an occupied hive and tried to move in. I saw the queen but was unable to catch her. The bees clustered on the front of the hive and were moving in the top entrance.
That evening after I got home from work I saw a small cluster of about 20 bees on a dead queen.
At dark I was able to see that there were no bees left in the bird house, all I could see moving in there was SHB. There was a patch of brood on three combs about five inches across but no bees and no SHB larva, very little pollen and no honey.
I froze the house for 26 hours and then opened it up and shook out the SHB. There was only about 60 beetles in the hive.
So, is that enough of an infestation to make the bees leave? Or ???
On a side note, I got a call for a swarm today that was the size of a baseball. Too small and too far to go get, but could it be the same problem? Curious isn't it?