What a difference in ventilation

[L Daxon]

Last year I added slatted bottom racks to all 3 of my hives and the bearding virtually disappeared overnight.

Yesterday, because we are in a dearth and I was afraid of robbing, I cut my hives entrances down by half after having them wide open since spring.  Tonight at dusk I noticed the most bearding on all of my hives that I have seen since putting the slatted racks on last year.  I am surprised what a difference in ventilation reducing the entrances by half made.  I guess tomorrow I will crack the tops a bit  to see if that helps with the air flow.

[BlueBee]

My bees are like yours ldaxon.  When I put a slatted rack under the brood nest, bearding goes way down or is eliminated.  I'm guessing the slats make room in there for the field bees to roost at night?  When I have a smaller bottom entrance, the bearding goes up again.  Changing the size of the bottom entrance has a big effect.

I have some hives running with bottom entrances and some with top entrances.  I get way more bees hanging out on the landing board in my bottom entrance configurations than the top/mid entrance hives. 

My hypothesis is a top entrance hive can be more easily ventilated by the bees since heat rises.  I think the top entrance setup also gives the field bees lots of room inside to roost.  However having a bottom entrance covered with bees at night is good at keeping moths out.