I did mine very similar to what was done by the OP (couple of years ago) I had the four hives here at house that I put them on and my bees must be not as coordinated because I had hundreds trying to find their way in on anything with a screen bottom board. I modified it the following year and cut almost the entire top off the screen and they worked better. This year I did not even bother to put them on and I know the Yellow jackets robbed out one of the hives here at the house. (not certain what I will find in my other locations).
“Why do we fall, sir? So that we might learn to pick ourselves up” Alfred Pennyworth Batman Begins (2005)
I have a mixture of screened and solid bottom boards, and by the end of this past season I had some kind of robber screens on almost all of them - a few very strong hives never did get one. A few related observations...
Whenever you put a robber screen on an established hive some confusion will ensue. A lot of foragers and hive activity will make it look pretty bad - all of those bees that can't figure out how to get in. And if it is also bearding season you might think that none of them are making it in because so many of them are on the outside of the hive. But they are, you just have to let them work it out. Screened bottom boards aggravate this somewhat, because they might hang out under the hive too.
If you start a new hive from scratch - a split or whatever - and install a robber screen right off the bat there will be no confusion whatsoever. They will orient and know from the beginning how to get in and out.
Queens fly out, mate and return to a hive with a robber screen just fine. If there is an increased failure rate it is below what I can detect.
I believe that during the summer and fall dearths a small amt of robbing happens even if you have robber screens on all hives - maybe bees that drift are able to rob from their previous address - but it isn't life threatening.
Hives with screened bottom boards are noticeably more robber proof than those with solids - I think because with the solid BB it is very clear to any would be robbers where the hive entrance is, but the smell coming out of the Screened BB baffles more of them. This is not really such a factor that it would make me change to SBBs, but maybe just something to consider.
Robber screens keep yellow jackets and other predators out as well as robbing honey bees.
Dead or really sick hives will get robbed out even if they have a robber screen in place. I don't know why or how - although I have some theories - but they do. The point being - don't count on robber screens to prevent the spread of mites and diseases from collapsing hives.
Robber screens work for me - they turned a very major problem into a minor nuisance - mostly just the fact that when you open hives to inspect or harvest honey robbing can get really fierce very quickly, but at least when you close everything back up it stops pretty quickly if your hives have robber screens. They have made it much more feasible to take care of nucs during late summer.
5Y-25H-T-Z6b-0 winter losses in '14
Thanks David. Those are some really good points to ponder.
I plan on trying my hand at woodworking this winter, and robber screens will definitely be on the list to try.
Greg Whitehead, Ten Mile, TN
Blog - http://gregsbees.blogspot.com/
I plan to do some woodworking this winter too, and I have a simple idea that I plan to try.
If a robber screen is sized right it could be more or less permanently attached (w screws) flush with the lower edge of the hive body. Then when it is set on a bottom board a simple wooden entrance reducer like device could be used to block the gap so that the bees would have to go in and out through the robber screen.
I say, like an entrance reducer because a standard wooden entrance reducer can't be installed to completely block the entrance - so my idea is for it to have a single reduced opening on one side only, and then when you flip it 90 degrees it would completely block the entrance. If the reduced entrance was only 1-2 bees big it would help train the bees to use the robber screen entrance, and would also be an effective mouse guard in the winter.
This way you could very easily close the entrance to activate the robber screen or open it to do for example an OA vapor treatment or whatever. Also you could completely close the bees in and they would still be able to get some air through the robber screen.
5Y-25H-T-Z6b-0 winter losses in '14
I knew when they figured it out when one night it got cold (for here) and the next day cool and gloomy. All bees were inside the hive.
"Rule Three of beekeeping...Never cease to feel wonder" Laurie R. King--
March 2010; +/- 30 hives, TF