Adventures!
Went out to the pond a couple of days ago to clean the filter. My wife pointed out that there was a lot of activity at the hives. The weaker hive was in an all out fight with robber bees. I got the jacket, hood and gloves on quickly and grabbed an entrance reducer. Just a nasty battle out there. I got the reducer on, and also noticed that even with the fight, or maybe because of the fight, no bees even landed on me, much less tried to sting me.
I came back inside to look for further reminders and instructions via forums and trusty google. With severe robbing in progress, the drastic measures are apparently a must - blocking the reduced entrance with grass for a couple of days,(they'll apparently work their way out over a couple of days), and draping a wet sheet over the whole hive. I asked my wife which sheet I could use, and of course she said none of them, so I grabbed a beach towel, with her blessing of course, soaked it, and draped it over the entrance, after filling the entrance with grass.
There are a lot of different robber screen configurations out there which are supposed to be deterrents. Apparently they won't stop robbing in progress, but if you set them up ahead of time, they discourage robbing and maybe it never gets started. The basic concept seems to be that the robbers are attracted to the smell of the honey, and fly straight to that smell, and the hive's bees are attracted to their queen and hive, and they will continue to try to find a way in if the direct route is blocked. The robbers get confused when the direct route is blocked and eventually are discouraged enough to stop trying.
The next day I took off the towel because there were no more robbers around and I unblocked the reduced entrance as well. Probably fifty or so bees marched out of the reduced entrance, two by two. Not sure if they were robbers that had been trapped inside, or hive bees that were annoyed that they couldn't get out and work. Of course I did this because I'm new to this whole thing and didn't think or realize that the robbers were still checking on a regular basis, so eventually they were back. At least this time I was a bit more prepared and put the wet towel back on. I do see bees working their way around the towel and a few right on the front where the direct route should be, so it appears to be working.
I'll leave it that way for a few days, and I think that if the weak hive survives this, I'm going to combine the two hives, rather than risk those bees getting completely killed off.