> >Do the bees recycle some of the moisture as they need to dilute the honey
> to digest it?
That's a reasonable assumption, Chris. Relative humidity would be quite
low in the center of the winter cluster, due to its temperature being
raised. Crude data from Simpson (1950) suggest that the dew point of the
cluster atmosphere is very close to the temperature of the insulating shell
of bees. Although he didn't observe condensation, those heat-generating
bees would likely experience enough moisture to digest honey.
Another paper by Simpson (1961) goes into more detail:
" Where winters are cold, the advantages of thermal protection may out-
weigh the disadvantages, particularly as a moderate rise from a very low
tem perature can give little increase in absolute humidity or opportunity
for flight. Where winters are mild, easy entry for heat may be more
important. Experiments [unpublished] indicate that when insulation is
minimal very free venti lation is necessary to avoid condensation. Bees
indigenous to the mountain ous regions of the Caucasus, where winters are
very cold, contract the en trances of their nests with propolis in the
autumn, and bees of western Europe do not. This may be an adaptation to
climatic conditions."
I find this discussion to be of great interest. Simpson's findings suggest
that there is no one-size-fits-all recommendation for ventilation and
insulation, since it is so dependent upon ambient temperature, humidity,
and length of confinement. As I review various regional recommendations,
two regularly keep popping up--top insulation, and a small flight
entrance/ventilation hole at the level of the winter cluster (as opposed to
at the top). Such an entrance allows cleansing flights, as well as the
altruistic self removal of sick or dying bees. It also allows the bees to
regulate the amount of ventilation by application of propolis to the upper
and lower entrances.
Przemek (or anyone else), have you used accurately-placed modern-day
humidistats to measure relative humidities at various points within and
without the winter cluster?
Simpson (1950) Humidity in the Winter Cluster of a Colony of Honeybees, Bee
World, 31:6, 41-44.
Simpson (1961) Nest Climate Regulation in Honey Bee Colonies. Science
133(3461): 1327-133.
--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com
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