Beehive energy budget

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Der Alte Fritz 

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Taking Jurgen Tautz's book "The Buzz About Bees", I thought I would use some of his facts and figures to work out an energy budget for a bee colony.:cheers2:

Queen lays 200,000 eggs a year which gives a population of around 50,000 in the summer and 20,000 in the winter.

1 bee collects 30 mg nectar (500 Joules) and makes on average 7 flights a day (using 10 J per flight) and works for around 15 days. So our forager produces 50,000 J and as there are 150,000 bees a year this translates to:

15 million foraging flights a year from the colony. 12 million for nectar, 2 million for pollen and 1 million for propalis and water.

Since our forager collects 30-40 mg nectar or 500 Joules, this translates to:
360-475kg nectar or 6,000 MJ of energy.

On the pollen side this forager collects 15mg pollen which builds up to 30 kg of pollen a year.

At this point Tautz's figures hit a problem as his mid range figures suggest that the average hive actually collects 3-4,000 MJ or 600kg of nectar but the 500 Joules figure gives us 6,000 MJ or around double. But we will work with his stated 4,000 MJ figure as the flight information is based on averages.

The colony collects 600kg of nectar which it reduces down to 300 kg of honey after evaporation. 1 kg of honey burns to produce 12 MJ so the colony has 3,600 MJ available

Energy expenditure

Summer:
Heater bees warming the brood use 2,000 MJ (166 kg of honey)
Other task use under 1,000 MJ (80 kg honey) or under 1/3rd.

Winter:
heater bees warming the colony use 2 MJ - (I think Tautz has this wrong. Beekeeprs would leave 15kg of stores on an average hive which translates to 180 MJ) So I will use 200 MJ.
Other tasks use under 50 MJ

Total budget 3,000 MJ in summer (250kg of honey) and 250 MJ in winter (21kg honey). The beekeeper takes his tithe of 300MJ (25kg of honey) or around 8% of the colony's energy turnover


These other tasks can be estimated as follows:
Energy used by foragers flying to collect nectar: 150 MJ
Food ???????
Royal Jelly production: 5 litres a year costs ?????
Comb production: to build a complete nest of 100,000 cells uses 1200g of wax or 90 MJ 0r 7.5kg of honey. This may be true for a swarm but in subsequent years, comb may only be replaced every 3-5 years, so reducing this down to 30 MJ or 2.5kg honey

If anyone can fill in the gaps to these other figures that would be great.
 

derekm 

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Too many invariables ....

in a PERFECT system perhaps !
I think its useful just to have a feel for the orders of magnitude involved...
There is tremendous about of energy expended during the summer in heat regulation.. it makes one think one should insulate for the summer more than the winter! But one would also have to ensure you did increase the heat expenditure on cooling the hive.
 

itma 

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Excellent topic! not worthy :hurray: :cheers2:


...

Total budget 3,000 MJ in summer (250kg of honey) and 250 MJ in winter (21kg honey). The beekeeper takes his tithe of 300MJ (25kg of honey) or around 8% of the colony's energy turnover
...


Comb production: to build a complete nest of 100,000 cells uses 1200g of wax or 90 MJ 0r 7.5kg of honey. ...
I'm actually looking forward to going through the workings ... :rolleyes:

But these conclusions leap out at me.
So, on those figures, reducing the summer energy expenditure by 1/10th could double the honey profit ...
... and doing a shook swarm (for complete brood comb change) might cost 1/3 of the standard annual profit - just in wax alone, regardless of brood disruption (negative to profit) and varroa reduction (positive to profit).

The summer in-hive energy expenditure stands out as being the big 'cost'.
It would be reduced by poly hive and white roof. What else? Anyone ever tried anything for cooling like those automatic greenhouse vent-openers? Or a little solar water pump for evaporative cooling? :bigear:
Seems like there might be a lot of things one could do with a prospective 1-year (or less) payback ...


I fully realise that there will be many who may say that stronger colonies and better management would boost yields by more.
But I'd suggest that anything like that could and would be additional to any 'energy-saving measures' ...
 

derekm 

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Is there any account of the embedded energy in 200 thousand dead bees?

RAB

Residual energy: thats easy 200,000 x 0.09gm x 1.25Kcal/gm x 42000 = 9.45MJ

cant find the calorific value of bees but crickets are about 1.2Kcal/gm

But did you mean the energy invested in creating them?... thats different
 

derekm 

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Working from uk average temp figures, the heat loss of a standard wooden (langstroth) hive, possible rate of build up of brood, possible heat loss from brood to hive...other fudge factors I come up with ~1000MJ for the summer (march sept) heat budget, which is the same order of magnitude.
Anyway a big chunk of honey in the summer goes to keeping them warm... how much you can get back by insulating is debatable.
but the difference in heat loss between a wooden hive and 40mm polystyrene in summner is equivalent by my calcs to ~ 80kg of honey. But the bee behaviour is the wild card perhaps some here wil say what difference they really see...

The one piece of research I read saw no improvement in honey production through insulation... So its more complicated
 
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Der Alte Fritz 

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Too many invariables ....

in a PERFECT system perhaps !
Not really, this is what the science of Ecology is all about. It uses probability, averages and statistics to give you a broad over view of how a system works - it will not hold true for any particular system but you can get an idea of how typical ones perform.

I take a couple of things from these figures
1) The high cost of brood production in summer. The bees maintain a very tight set of parameters but could we help them in some way? Even small changes would bring quite big rewards in terms of honey storage.

2) What these figures do not show is the effect of timing and seasonality. Nor do they show what might be the factors for optimal success for the colony when adjusting timings. Does a big brood equal more honey collected? Anecdotal evidence is that large colonies perform better and bring in greater surpluses. What is unclear is whether a big brood always reaps a bigger reward since it is all about the timing - if the big group of foragers miss the main crop, then they become more of a burden than a gain?

3) The critical spring growth. A colony has a small "old" workforce in the Spring and few honey reserves. The queen starts laying and very quickly you have a lot of energy being spent on warming that brood (often in adverse weather conditions - so really expensive!) you have only a small workforce to both forage for fresh stores and heat the brood. The figures show what a heavy drain this is on the colony. So there is probably a reverse feedback loop to prevent colony collapse by laying too much brood and then running out of honey to bring them to maturity. So to get a rapid colony growth in the Spring and hence a big work force in the best part of the summer, you need to have a good supply of stores at the end of the winter. Perhaps a Spring harvest might be a better option?
 

Der Alte Fritz 

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One of the figures missing from this model is the cost of the bees eating to sustain their normal activity.

But let us have a go. The winter population of bees is around 20,000 and we know they do little activity (their heating activity is covered under a different figure) other than the odd cleansing flight, moving around and existing. This costs under 50 MJ. So each bee expends 0.0025 MJ for 6 months activity.

a) For the total population of bees of 200,000 for a year this would equal 0.0025 x 200,000 x 2 = 1,000 MJ. This seems about the right sort of number since we know they have 1,000 MJ in summer and 50 MJ in winter for 'other activity'. Certainly on the high side but the right order of magnitude. This accounts for under 80 kg of honey.

b) The drone population is often seen as a burden and we try to limit drone production but in reality what do the drones cost? A normal population of drones is around 10,000 for 6 months of the year. At 0.0025 MJ per bee this comes to 25 MJ or 2 kg of honey or two thirds of 1% of the total. Their main job is flying and they make around 3 flights per day. Drones live for 90 days and are sexually mature after 38 days so we could expect them to fly for 50 days. So the number of flights equals 10,000 x 3 x 50 = 1.5 million flights. At 10 J per flight that equates to 15 MJ or 1 kg of honey. (We could add in this 1.5 million flights total to our too high number of flights - 12 million nectar flights to reduce the imported energy into the hive)
So total cost of drones is around 40 MJ (eating and flying) or 3 kg of honey or 1% of the total energy budget of the hive. Given the cost of rearing queens is so low given their small numbers, this is a very efficient reproductive cost in energy terms in the animal kingdom where there are often huge costs in transfering gametes and sexual display.
Add in the drones role as heater bees and they are looking as very good value for money!
 

Der Alte Fritz 

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Incidentally this view directly contradicts research done by TD Seeley in 2002 which showed that colonies with a low drone population, produced more reserves by the end of the season 45 kg compared with those that had a normal population 25kg. This was always taken to mean that the cost of drones was quite high (ie the difference between the two or 20kg of honey) But this is taken from a simple in/out type of energy balance and clearly has no bearing on the actual 'cost' of the drones. If it did and a small population of 10,000 costs 20 kg then the full colony of 200,000 would cost 400kg which is way too high and includes no cost of heating the hive, etc, etc.

The correct conclusion is more likely to be that if you tamper with the population balance of a colony, the bees behave differently. Whether this is good for their health is another debate.
 

alanf 

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interestingly Seeley mentioned in his NHS talks that wild colonies have lots of drones (upto 20% drone comb).
Is this indigenous or native bees rather than feral? Sounds reasonable, wild population genes will gain an advantage in being spread. Stores need only be enough for the colony; excess is a liability, it needs space and maintenance as well as attracting predators.
 
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oliver90owner 

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Stores ... excess is a liability, (with reference to 'wild' colonies)

I would tend to disaree in most instances.

An excess means there were good foraging crops/favourable seasonal weather and a strong colony in the preceding period.

That excess is always stored where the bees can most easily defend it - above the brood nest (in the average vertical cavity). It is insurance against a poor season the following year. It will only be there if there is adequate space, and will effectively reduce the unused space below the brood nest/cluster, which may have an advantage.

Only having enough can easily change to not having quite enough - with the simple consequence being starvation, and a lost colony.

Only enough may mean spring expansion is limited leading to a lower chance of reproduction in that season (or early enough for the swarm to become secured in the new home with adequate stores for the coming winter).

All in all, I reckon an excess is an asset, not a liability.

RAB
 

alanf 

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"Is this indigenous or native bees"

we're talking US of A so feral.
Is this based on one of his books? Suggests selective pressure to up the drone percentage emerges over relatively few generations. From the beek perspective it means anyone operating in a high feral population area is going to have a lot of these drones mating with their queens.
 

Der Alte Fritz 

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interestingly Seeley mentioned in his NHS talks that wild colonies have lots of drones (upto 20% drone comb).
Yes he does but also makes the point that drone brood is used for a much shorter period of time during the year and that the 20% refers to "area" and since drone brood is a little bit larger than worker comb, this would result in under 20% drone bees. Coupled with the shorter season this would mean a population of between 10-15% of drones.

The 10,000 figures I used was an average for framed hives ie managed, where the drone numbers are further reduced artificially.

But even a population of 40,000 drones would still not have a large energy.
 

Der Alte Fritz 

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