Here are a few short clips of what's happening on my hive these days. I find this behavior quite peculiar, although I can hazard a few guesses about what it means.
First, the front of the hive. Notice that there aren't a lot of bees hanging around. A few are busily going in and out through the top of the robber screen, and there is a clump of bees at the base (where they can't get in).
Next, the back of the hive. No entrance here, but it's *covered* in bees just sitting there. Some are going in and out at the space under the bottom board, but there's nowhere to go in there.
Finally, here's the side of the hive. Not much activity here, but at the base of the hive bees are running back and forth sniffing each other.
Now, my guess as an inexperienced new beek is that the guys on the back are would-be robbers, the guys on the front are (mostly) my bees, and the guys on the side are in a no-man's-land where the guard bees are confronting the robbers. Since I had a fairly serious robbing problem before I put in that robber screen, I'm hoping this is a good sign, but I don't know enough to be sure. Certainly I don't understand what all those bees are getting out of just sitting at the back of the hive twiddling their thumbs. What say you all?