Re: Hive swarming
"Open" screened bottom boards are associated with reports of absconding by package bees shortly after installation, and may very well be related to your reports of hived swarms leaving shortly after you unblock the hive entrance. It may be that the bees don't like the light, or the airflow, but the WHY isn't that important if they are motivated to abscond by open screens.
If you want to use screened bottom boards, close them off at least until the bees have brood to anchor them.
I built screens into my bottom boards, but do not leave them "open". They have oil trays beneath the screens, and the design effectively blocks bees from the tray and airflow from moving through the screen. An alternative to oil in those trays is lime or diatomaceous earth.
If you want more ventilation add a top vent instead of an open screen bottom.
Also, note that bees cool their hives via hauling in water and evaporating it - similar to a swamp cooler in a structure. If the outside air temperature exceeds 94 F, then having lots of [hot] air flowing through the hive works in opposition to the bees efforts at evaporative cooling.
Last edited by Rader Sidetrack; 08-02-2014 at 11:35 AM.
USDA Zone 7A Elevation 1400 ft