Re: ATTN: New beekeepers with screened bottom boards
Just to throw my minimal two cents into this discussion:
I have run screened bottom boards ("SBB") from day 1. I have never had a package, swarm, split, or any other type of hive abscond. Thus, I can say that SBB's have never caused any of my bees to abscond.
I like SBB's for the diagnostic benefit of looking at what and where detritus falls onto the board. This includes dropped wax flakes, dropped pollen pellets, dead mites, and wax moth poop. It is a helpful and easy-to-use tool, especially when looking at mite fall after an OAV or Apiguard application.
When I first started with bees, I used only a bottom entrance. I would pull out the SBB a few inches on especially hot days. But, now, I run a bottom and top entrance year-round. This is a huge benefit to the hive because it allows the bees (rather than an ignorant human) to easily adjust ventilation to however they want it through the year. Accordingly, I no longer use a SBB to adjust hive ventilation. In other words, my SBB are fully inserted year-round.
I also run all mediums and an open brood nest. The bees almost always run the brood chamber into the 3rd medium. A prolific queen in a good year will lay into the 4th medium. But, the bees almost never use the bottom medium box.
I am starting to wonder if not using the first box is due to the SBB being too drafty, even when it is closed. This makes me want to switch to a solid bottom board configuration, but I don't want to lose the diagnostic advantage of the SBB. Hmmmm . . . .
Also, don't forget that the effects of a SBB are very dependant on what your local climate is.
(1975-1980, and now since 2011; maintain about 10 hives; Zone 5b; 15" rain; 5500')