50% losses winter 2012/2013

[itma]

... The latter leaves a half inch ventilation gap across the width of the back of the hive.
If the hive is fitted with an entrance block or mouse guard then any wind blowing directly onto the back will be forced up through the hive because the entry area is bigger than the available exit.
Many hives face south so the problem winds will tend to be the colder ones from the north.

Err, not necessarily!

That could indeed be the case if there was an air outlet at the top of the hive, for example from the infamous matchsticks.
However, if the hive is fully closed above the entrance, then there would be no such up draught, because there is nowhere for any such flow to exit.

Using a sealed board is very close indeed to using a solid floor - and would best be reported as such!

 

[madasafish]

Err, not necessarily!

That could indeed be the case if there was an air outlet at the top of the hive, for example from the infamous matchsticks.
However, if the hive is fully closed above the entrance, then there would be no such up draught, because there is nowhere for any such flow to exit.

Using a sealed board is very close indeed to using a solid floor - and would best be reported as such!

Vortices will be formed in any such flow of air.. These will inevitably distribute some cold air inside the hive.. where and how much will need about 3 hours on a supercomputer and a wind tunnel...

 

[BeeJayBee]

The varroa mesh would reduce the strength of any air current - that's why windbreaks aren't solid.

 

[Fraise]

Some of the losses were quoted with ventilation at the top as well e.g.
" losses 100% on 11 14x12 hives with open feed holes, varroa board in"

So having hole at top as well as bottom could contribute to 100% loss.

 

[pargyle]

Some of the losses were quoted with ventilation at the top as well e.g.
" losses 100% on 11 14x12 hives with open feed holes, varroa board in"

So having hole at top as well as bottom could contribute to 100% loss.

Thats what it looks like but there'll be someone along shortly to say No !!

 

[user 6228]

: ...
Yes changing the materials for more or less inherent insulation will adjust the relationship between cluster size and survivable outside temperature, but only in so much as it adjusts the critical point in the relationship.

Do we know if clustering is good for a colony? Winter bees are raised to survive the winter, and they do this by a combination of body reserves and inactivity. They certainly seem to have adapted to a need to cluster over winter, given that this was not a feature in their original geography. What behavioural and physiological changes would occur in an over-wintering colony that was so toasty it didn't need to cluster? How much stores would they need? I assume that if they're doing more (metabolically) they'll need to take cleansing flights more often... and if it's still sub-zero outdoors, what happens then? ..... "

.. ....

My experimental studies indicate that in their typical natural habitat they are not forced to cluster unless the outside temperature is below -25C. The shape and insulations of a tree nest will enable them to keep the top 10% of the nest space above the clustering temperature with a heat output that is easily within the capability of a moderately sized colony

In addition. I have measured an occupied hive insulated to tree nest standards with the floor area kept at 16C by the bees while the outside temperature is at -15C and bright (A moderate sized colony in january from a previous years split). In a period of very dull weather the colony let the temperature of the floor fall to close to ambient.
These "tree warm" colonies will fly on any bright cold day and will fetch water as soon as its above freezing

Bee cluster metabolic rates versus temperature and size are complex (E. Southwick).
The graph of whole bee colony metabolism descreases with increasing ambient temperature upto about +5c where it reaches a local minima it then increases with temperature to around 20C to a local maxima it then decreases to down to 35C.
Thus a bee colony providing it is in a nest that does not lose or gain excessive heat can control both its temperature and heat production over a wide range of ambient temperatures.
From my observations I hypothesise that bees should only need to cluster in extreme cold conditions, or when there is no opprtunity for activity (e.g. cleansing and water).

Note Polyhives are not sufficiently insulated to be "Tree warm"

 

[pargyle]

My experimental studies indicate that in their typical natural habitat they are not forced to cluster unless the outside temperature is below -25C. The shape and insulations of a tree nest will enable them to keep the top 10% of the nest space above the clustering temperature with a heat output that is easily within the capability of a moderately sized colony

In addition. I have measured an occupied hive insulated to tree nest standards with the floor area kept at 16C by the bees while the outside temperature is at -15C and bright (A moderate sized colony in january from a previous years split). In a period of very dull weather the colony let the temperature of the floor fall to close to ambient.
These "tree warm" colonies will fly on any bright cold day and will fetch water as soon as its above freezing

Bee cluster metabolic rates versus temperature and size are complex (E. Southwick).
The graph of whole bee colony metabolism descreases with increasing ambient temperature upto about +5c where it reaches a local minima it then increases with temperature to around 20C to a local maxima it then decreases to down to 35C.
Thus a bee colony providing it is in a nest that does not lose or gain excessive heat can control both its temperature and heat production over a wide range of ambient temperatures.
From my observations I hypothesise that bees should only need to cluster in extreme cold conditions, or when there is no opprtunity for activity (e.g. cleansing and water).

Note Polyhives are not sufficiently insulated to be "Tree warm"

Fascinating stuff Derek - Have you an idea of what the preferred temperature of an overwintering colony at the top of the hive is ? Does it vary with external temperature or do they try to maintain a constant temperature ?

 

[sunhivebee]

My experimental studies indicate that in their typical natural habitat they are not forced to cluster unless the outside temperature is below -25C. The shape and insulations of a tree nest will enable them to keep the top 10% of the nest space above the clustering temperature with a heat output that is easily within the capability of a moderately sized colony

In addition. I have measured an occupied hive insulated to tree nest standards with the floor area kept at 16C by the bees while the outside temperature is at -15C and bright (A moderate sized colony in january from a previous years split). In a period of very dull weather the colony let the temperature of the floor fall to close to ambient.
These "tree warm" colonies will fly on any bright cold day and will fetch water as soon as its above freezing

Bee cluster metabolic rates versus temperature and size are complex (E. Southwick).
The graph of whole bee colony metabolism descreases with increasing ambient temperature upto about +5c where it reaches a local minima it then increases with temperature to around 20C to a local maxima it then decreases to down to 35C.
Thus a bee colony providing it is in a nest that does not lose or gain excessive heat can control both its temperature and heat production over a wide range of ambient temperatures.
From my observations I hypothesise that bees should only need to cluster in extreme cold conditions, or when there is no opprtunity for activity (e.g. cleansing and water).

Note Polyhives are not sufficiently insulated to be "Tree warm"

Thank you very much. What amazing research!

 

[user 6228]

Fascinating stuff Derek - Have you an idea of what the preferred temperature of an overwintering colony at the top of the hive is ? Does it vary with external temperature or do they try to maintain a constant temperature ?

The whole field of bee behaviour in a "Tree warm" environment is unexplored
as research has either been Isothermal i.e. a forced temperature or high heat loss (i.e. wooden hives).

My small amount of investigation indicated they keep a prefered temperature only when activity is possible( bright days occuring without extended periods of dullness or brooding) otherwise they go into "standby" i.e. clustered energy conservation.

Further research required.
In addition bee toxicology and parasite behaviour in "tree warm" environment is unexplored. Thats the reason we didnt treat last Autumn or Winter. We didnt know what would happen.

 

[user 6228]

Some of the losses were quoted with ventilation at the top as well e.g.
" losses 100% on 11 14x12 hives with open feed holes, varroa board in"

So having hole at top as well as bottom could contribute to 100% loss.

I can tell you it causes a substantial increase in heat loss although less than the infamous matchsticks (measured).
Note small details in the roof construction can make significant differences to the air movement and consequent heat loss.

 

[PBee]

I'd be really interested to hear more, PBee

The polyhives were mostly on solid poly floors with a tight fitting 50mm kingspan crownboard/poly feeder and poly roof. The entrance had a plastic mouseguard as in the photo. I had expected there to be a lot of condensation, but as long as the cluster was the right size the hives remained remarkably dry. The Nicot plastic hives were set up with a kingspan crownboard but were more often damp on the walls, outside frames and the periphery of the crownboard. I had six double brood Nicot colonies which had been drone providers and brought back late so left in the double format. These were clustered very tightly any time I checked and came out of winter with slightly smaller clusters but rebounded and were of similar strength to the polys in May.

A paper in the latest JAR has some references to research done on the benefits of restricted ventilation in winter.

Some researchers have successfully overwintered bees in conditions of limited ventilation. In experiments with colonies which had closed hive entrances food consumption and bees’ mortality decreased, and the amount of faeces in the hindgut of bees decreased 15.0% on average and up to 37.6% maximum as there was no free flow of cool air into the hive and the bees were calm (Perepelova, 1947). Similar results were obtained by Michailov (1964). In his experiments, the wintering of honey bee colonies was most successful inside a building. In this case, both entrances were closed and the colonies were covered on top with a cover cloth only. The upper entrances were opened on 20 February when brood emerged in the colonies. Colonies with weak ventilation consumed 15.6% less food and reared 54.1% more brood in spring. Later experiments with 227 colonies in two winters confirmed the results: poorly ventilated colonies consumed 0.8 kg (7.0 and 6.6%) less food on average, had fewer dead bees in winter and reared more brood in spring (Michailov, 1964). It shows that weak ventilation reduced heat loss and created more favourable conditions for the bees, reducing the metabolism level, food consumption and mortality of bees and helped to preserve their energy for spring development.

http://www.ibra.org.uk/articles/Water-vapour-descends-from-the-winter-cluster

Way too much ventilation? .....

 

[user 6228]

A paper in the latest JAR on has some references to research done on the benefits of restricted ventilation in winter.
http://www.ibra.org.uk/articles/Water-vapour-descends-from-the-winter-cluster

Way too much ventilation? .....

doing this with out a discussion on the effects of insulation invalidates the results... insulation has a dramitic effect on condensation and the stress on the inhabitants from the condensation

 

[PBee]

If you are referring to the ventilation research then I assume they used standardized equipment to study the effect of reducing ventilation so the results should be valid for those parameters.

 

[user 6228]

If you are referring to the ventilation research then I assume they used standardized equipment to study the effect of reducing ventilation so the results should be valid for those parameters.

not really, as the lack of insulation adds more than one level of stress.
ie. higher condensation higher stress due to heat loss plus higher heat loss due to condensation that is higher.

The difference is so large that your assumption will need experimental justification.
that doesnt say you are wrong just not proven

 

[Finman]

The difference is so large that your assumption will need experimental justification.

Inventing a wheel again

.

 

[Finman]

My experimental studies indicate that in their typical natural habitat they are not forced to cluster unless the outside temperature is below -25C.

Note Polyhives are not sufficiently insulated to be "Tree warm"

What a rubbish!!!

And where you got -25C out temps? And how long was that period.
These temps are rare even in Finland,

 

[user 6228]

What a rubbish!!!

And where you got -25C out temps? And how long was that period.
These temps are rare even in Finland,

I have experimentally(with scientific rigor )measured the thermal conductance of various hives and a thermal model of a tree at the typical power output of a medium sized colony. Some of these hives were made in Finland

 

[Erichalfbee]

Thanks PBee
Much to think about

 

[Tom Bick]

I have experimentally(with scientific rigor )measured the thermal conductance of various hives and a thermal model of a tree at the typical power output of a medium sized colony. Some of these hives were made in Finland

Not totally disagreeing with you Derek but there must so many variables I would be interested on the model you base your findings.

 

[user 6228]

Not totally disagreeing with you Derek but there must so many variables I would be interested on the model you base your findings.

The dimensions of the tree cavity model were taken from the survey of tree nests by Tom Seeley. The dimensions of the cavity and the wall thickness were adapted to a national volume ~30 litres. The walls were made from foam thickness that would give the same insulation properties of about 9" of oak or about 4_5" of cedar.(using the correct formula for heat transfer in a cylinder). The tree model was fitted with a resistaince heater and 8 temperature probes. I am going to do some further measurements to investigate different points in the size /shape distribution reported by Seeley.(once the beekeeper returns to look after her swarms . If you can get down to either portsmouth or bournemouth in the autumn I'm doing some talks at LBKAs on the experiments.