Last weekend I was watching my home-based hive from my living room window with binocs, as usual. Lots of bees - but one or two were darting at others as they came in. Watched closely. There were a few more apparent tussles going on. The incoming bees took on the appearance of a fleet of incoming fighter-bombers, weaving slightly but steadily entering the hive. I was sure this meant robbing was going on. I think it may have been going on for some days, as at the previous inspection I noted some completely empty frames and a lower number of bees, but I put this down to reduced brood rearing and that they had used up some of their supplies, it being late in the season and not much flowering.
I made up an anti-robber screen with some #8 and strips of wood and fixed it over the entrance (this was at about 2 pm). Soon a mass of bees built up all over the lower part of the entrance -hundreds of them. Exiting bees were scrambling out steadily for a while then dwindled off. There were a lot of bees hanging about and crawling all over the hive the rest of the day. Later on some friendlies showed up with pollen loads but I did not intervene as there were obviously more robbers still there. Next morning no bees seen outside, so where they all went in the end I don't know. No bees were going in the screen valve. I did not block the upper entrance notch in the inner cover and a few bees probably went in there.
Next day I left the screen on until an hour before dusk, then removed it to let the local bees get in. The past 2 days I have left the screen on 24/7, but I don't know if I should, or really what the state of play is now. If I take it off, will the robbers just start back up again? Or is leaving it on too much of a disadvantage to the home bees? I can't observe things in the week as I am at work. When I leave they have not come out, and when I'm back they're usually in for the day , so who knows what's happening.
ideas appreciated -thanks,