>> I think most UK beekeepers would find the idea of a top entrance really
>> strange - even alarming - and your bees seem to agree.  Why do you use
top
>> entrances (as heat rises) and do they replace the bottom entrances?

> (New England, US), we can easily have 1 meter or more of snow on the
ground for several months...

Most places East of the Mississippi River and South of Boston, MA have not
had much snow in years, but we do have humidity.  It is this damp that we
want to vent.  The bees make plenty of condensation with their respiration,
so there's a limit to what we want to see build up in a hive.  The classic
symptom of a lack of top ventilation is a saturated inner cover or one
stained from prior saturation on those occasional winter days warm enough
for the bees to fly when beekeepers nervously check for brood and stores. 

There are all sorts of wacky approaches to trapping this moisture, but they
are all inferior to a small vent, a notch in the inner cover, no wider than
my thumb.  Many of these approaches trap moisture, allow it to condense, and
then drip it back onto the cluster.  While cold alone does not kill bees
often in any but the farthest-North states, the combination of moderate cold
and water dripping on bees certainly can.

There are many who point to bees in hollow tree cavities as the ideal model
for "what bees prefer", but this is a common error, as it mistakes bees
making do with what is available for bees actively showing a preference.
Perhaps one of the reasons for such low first-winter survival rates for
swarms "in nature", and one reason why feral tree colonies are so often much
smaller than those that move into wall cavities is that nature rarely
provides a good hollow tree trunk with top ventilation, while cavities in
man-made-structures often do.

"Nestduftwarmebindung" is a strong endorsement for blocking any top vent. It
is fun to say, but hard to pin down in terms of how it is supposed to offer
tangible benefits to a hive that can be measured with impartial metrics.

But there is such a thing as too much vent.  I messed around with hive
toppers that had light-trap baffles combined with various amounts of vent,
and trying to help the bees the evaporate more nectar with passive "solar
chimney"-driven air circulation schemes, and even when the bees were in the
middle of a bloom, they would take the time to plug the much of the
screening on these vents with propolis.


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My typo rate may vary
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