I wish I had fully opened the hive to see if there were dead bees inside. Seems like it about has to be a brand new swarm has moved in. I don't *think* when bees swarm that the entire colony abandons the hive - I think the new queen and some of the workers stay in the old location. If the old colony died, it might mean this new colony is doomed, and maybe will spread whatever killed the others.

I can see where a hive with honey would draw a new swarm, and I don't think they were robber bees from a different colony harvesting the abandoned honey. It was right at dusk when I noticed them and they were obviously headed into the hive for the night. (Swarming bees are pretty common here. There is an old house a block or two away whose walls have housed a massive colony of bees for a long, long time. That is probably where the earlier swarm, as well as this one, came from.)

I'm pretty sure we have some beekeepers among us. Hope one of them notices this thread.