Weight for spring

I’m currently reading The Lives of Bees by Thomas Seeley. It’s a very good account of honey bee colonies in the wild.

In the book Seeley describes studies he conducted in the early-80’s on the changes in weight of unmanaged colonies during the season 1.

One particular figure caught my attention as I was off to the apiary to heft 2 some hives and check on the levels of stores.

Colony weight (top) and weekly weight change (lower). Black arrows midwinter, red arrows early spring.

The upper panel shows the overall hive weight over a period of ~30 months, including three successive winters. I’ve butchered annotated the figure with black arrows to mark the approximate position of the winter solstice and added red arrows to indicate early spring (approximately mid-February i.e. about now) 3.

Look carefully at the slope of the line. In each year it steepens in early spring.

Shedding pounds

During the winter the colony survives on its reserves. There’s no forage available and/or it’s too cold to fly anyway, so the colony has to use honey stores to keep the worker bees alive.

In late autumn and early winter they can get by using minimal amounts of stores, just sufficient to keep metabolic activity of the bees high enough to maintain a cluster temperature of ~10°C.

All of this uses stores and so the colony gradually loses weight.

Frosty apiary

Frosty apiary

The weekly weight gained and lost is shown in the lower panel. In 1981/82, with the exception of a tiny weight gain in late August, the colony lost weight every week from mid-July until mid-April (9 months!).

But from mid-April to early-July the colony literally piles on the pounds 4.

To achieve this they need a strong population of worker bees. It’s not possible to collect that much nectar with just a few thousand bees. The colony must undergo a large population expansion from the 5,000-10,000 bees that overwintered the colony to a summer workforce of 30,000+.

This expansion is not simply the addition of a further 20,000 bees. At the same time as the new workers are emerging the winter bees are dying off. The colony therefore needs to rear significantly more than 20,000 bees to be ready to exploit the summer nectar flow.

And, since it takes bees to make bees this means that the colony must rear repeated cycles of new workers starting in very early spring.

But you can’t rear brood at 10°C

Brood rearing requires a cluster temperature of ~35°C. This is achieved by the bees raising their metabolic activity, repeatedly flexing their flight muscles and generating heat.

All of which uses lots of energy … which, in turn, is derived from the honey stores.

Which explains why, in early spring, the rate at which stores are consumed suddenly increases. And the rate at which the colony uses the stores is the weight lost per unit time i.e. the slope of the graph shown above, or below for emphasis.

Colony weight in early spring

Of course, some of the honey stores are also consumed by the developing larvae. How much presumably depends upon the amount of brood being reared and the external temperature.

Less brood requires less honey stores. Lower temperatures mean more energy must be expended to keep the brood at 35°C, so more stores are used.

Rearing brood also requires protein (pollen). Nearly 90 years ago Clayton Farrar studied the spring weight loss of colonies in Wisconsin maintained with or without pollen stores. Colonies unable to rear brood because they lacked pollen used ~50% less stores over the same period.

Thermoregulation is energetically costly and colonies must raise the temperature of the cluster to ~35°C in very early spring to rear sufficient brood to exploit the late spring nectar sources 5. They need to maintain these elevated temperatures – using yet more stores up – until the spring nectar flows start.

The danger zone

All of which means that we’re currently approaching the danger zone when colonies are much more likely to starve to death if they have insufficient stores.

The next six to eight weeks or so are critical.

If they have ample stores they will rear plenty of brood.

Clear evidence for brood rearing on trays under colonies in the bee shed

If they have borderline levels of stores they might be able to maintain viability of the colony, but they’ll only achieve this by not rearing brood 6.

If they start brood rearing and then run out of stores they will likely starve to death.

Winter chores

Every couple of weeks I check all of my colonies.

I confirm two things:

  • the entrance is clear i.e. not blocked with the corpses of dead bees.
  • the colony has sufficient stores for another few weeks.

This takes no more than one minute per colony and can be done whatever the weather, or even at night if you cannot get to the apiary in the short daylight hours.

Bent bicycle spoke to keep entrances clear

The floors I favour have an L-shaped entrance tunnel which during extreme periods of confinement can get blocked with dead bees. A quick scrape with a bent piece of stiff wire clears them away.

Even ‘normal’ entrances should be checked as it’s surprising the number of corpses that can accumulate, particularly after a long period of very adverse weather when no undertaker bees are flying.

As an aside, assuming no brood rearing, a colony entering the winter with 25,000 bees will likely lose an average of ~150 bees a day before brood rearing starts again in earnest. They will not be lost at the same rate throughout the winter. Do not worry about the corpses (though it’s worth also noting that a strong, healthy colony should clear these).

Hefting the hive

The weight of the hive can be determined in at least three different ways:

  1. wealthy beekeepers will use an electronic hive monitoring system with integral scales. No need even to visit the apiary to check these 😉 Where’s the fun in that?
  2. thorough beekeepers will use set of digital luggage scales to weigh each side of the hive, summing the two figures and noting the total carefully in their meticulous hive records.
  3. experienced beekeepers will briefly lift the back of the hive off the stand and decide “Hmmm … OK” or “Hmmm … too light”. This is termed hefting the hive.

If this is your first winter I strongly recommend doing the second and the third method every time you visit your apiary.

The second method will provide confidence and real numbers. These are what really count.

Hefting the hive for comparison will, over time, provide the ‘feel’ needed to judge things without a set of scales.

Over time you’ll find you can judge things pretty well simply by hefting. I do this 7, but only after removing the hive roof. I’ve got a variety of roofs in use – deep cedar monstrosities, dayglo polystyrene and lots of almost-weightless folded Correx – which, coupled with the variation in the number of boxes and the material they’re made from, complicates things too much.

Without the roof I find it a lot easier to judge.

Hmmm … too light

Anything that feels too light needs a fondant topup as soon as possible.

If you even think it feels too light it’s probably wise to add a block of fondant.

You need to use fondant as it’s probably too cold for bees to take down syrup. Fondant works, whatever the weather.

How much fondant should you add?

Look again at the hive weight loss per week in the early months of the year in the lower panel of the first graph. These colonies lost at least 1-1½ lb per week.

When will you next check them?

Do the maths as they say …

If you check them fortnightly you really need to add 1-2 kilograms which should be sufficient to get them through to the next check. Do not mess around with pathetic little 250g blocks of clingfilm-wrapped fondant. They might use that in three days …

You also don’t want to be opening the hive unnecessarily. Add a good-sized block and let them get on with things.

Recycle

Loads of supermarket foods are supplied in a variety of clear or semi-translucent plastic trays – chicken, mushrooms, tortellini, curry ready meals etc 8. Throughout the season I wash these out and save them for use with the bees.

I stressed clear and semi-translucent as it helps to be able to tell how much of the fondant the bees have used up when you’re trying to judge whether they need any more.

Waste not, want not

Many of these trays are about 6″ x 4″ x 2″ which when packed with fondant conveniently weighs about a kilogram. I fill a range of these with fondant, cover them with a single sheet of clingfilm and write the weight on the clingfilm with a black marker pen.

Location, location, location

In the winter the goal should be to locate the fondant block as close as possible to the cluster.

This means directly over the cluster.

Not way off to one side because there are fewer bees on the top bars that are in the way.

There’s no point in adding fondant if you also force the bees to move to reach it.

You’ll need an eke (or a nice reversible, insulated crownboard) to provide the ‘headspace’ to accommodate the fondant block 9.

Fondant block directly over the top of the cluster (in this case on a queen excluder)

Don’t delay.

Don’t wait for a ‘nice’ day.

You’ve decided the colony is worryingly light so deal with it there and then.

Remove the roof and the crownboard. If it’s cold, windy or wet the bees are going to be reluctant to fly. Don’t worry, you’re helping them. You’ll do more harm by not feeding them than by exposing them to the elements for 30 seconds 10.

Remove the clingfilm entirely 11 and invert the plastic tub directly over the top of the cluster.

Add the eke. Replace the crownboard, the top insulation and the roof.

Job done.

Crownboards with holes and queen excluders

Some crownboards have holes in them. Often these in the centre of the board.

It’s often recommended to add the fondant block above the hole in the crownboard. I think it’s better to place the fondant directly onto the top bars for the following reasons:

  • the central hole in the crownboard is probably not above the cluster 12. Why give them more work to do to collect the stores you’re providing?
  • it’s cold above the crownboard. The bees are less likely to venture up there if it’s chilly and uninviting.
  • fondant deliquesces (absorbs moisture) and can get distinctly sloppy when located in the humid headspace above the crownboard. In contrast, if the fondant is on the top bars of the frames any moisture absorbed softens the fondant surface at exactly the point where the bees are going to eat it anyway.

Finally, if there’s any reason you need to go through the brood box (before the fondant is finished) place the fondant on top of a queen excluder directly over the frames. Fondant has a tendency to stick down firmly to the top bars and it’s a nightmare to remove it to get to the frames. In contrast, if it is on a queen excluder you can easily lift it off.

You might not need to do this, but I learnt the hard way 🙁


 

Footnotes

  1. This was prior to the introduction of Varroa to North America. An unmanaged colony is a wild-caught swarm housed in a Langstroth hive with no active management – swarm control, feeding etc. – and inspected rarely solely to monitor colony development.
  2. To lift for the purpose of trying the weight … which the OED state was first used in c. 1816. Etymology from heft n. and heave … analogical: compare weaveweftthievetheft etc.
  3. With apologies for the quality of the image. The original paper was published in Ecological Entomology. My library has a subscription … but only as far back as the end of the last century. Shame on the journal for keeping a paper published almost exactly 35 years ago behind a paywall!
  4. Remember, these hives were in New Haven, Connecticut … the specific timing of nectar flows will vary depending upon location. In Scotland my colonies gain weight through May, usually lose weight in mid/late June and then build up again during the summer flows in July.
  5. Which, in turn, are what are used to build big booming colonies that swarm = colony reproduction. Of course, for the beekeeper, it is these colonies that pile in lots of honey and are probably better able to defend themselves against both diseases and robbing.
  6. Meaning the colonies will build up slowly when forage does become available and are unlikely to be strong enough exploit early nectar flows.
  7. After years of weighing colonies and with a few linked up to an Arnia system.
  8. These are examples and are not necessarily representative of my diet.
  9. Use a spare super if you’ve nothing else, but consider packing the empty space with bubble wrap.
  10. Generally, the worse the weather the less chance you’ll need the smoker.
  11. Bees chew it to shreds and drag it down into the brood nest.
  12. The winter cluster is often centre front of the hive.

21 thoughts on “Weight for spring

  1. Sheila Kitson

    I am finding this information most useful as a beginner beekeeper. thank you.
    Please what is FONDANT?
    Can I continue with white sugar feeding? The temp. is 4 c. (38 F)during the day
    I am in BC. Canada the hazelnut catkins will soon be available with pollen
    The crocus are not far behind.
    When the sun is out there ate some bees that are out for a “flyaround” Lots of rain this past month though.
    Thank you for your help.
    Sheila Kitson

    Reply
    1. David Post author

      Hello Sheila

      Fondant is the stuff bakers use on iced buns … it’s essentially cake icing. I buy it by the block (actually, 200kg at a time) and use it for almost all of my feeding. If you just feed white sugar the bees will also need water to take it down and process it. At 4°C the bees barely be flying.

      If the colony has ample stores it will not need any additional feeding. Hefting helps determine this.

      It’s very difficult to give advice for the other side of the world (without knowing the local conditions). Is there a local experienced beekeeper you can ask?

      Pleased you find the information useful.
      Regards
      David

      Reply
  2. vince poulin

    Another very informative post especially important for those of us lucky to be seeing first ever over-winter colony successes. This may be of interest to many. This summer I successfully grafted and reared 4-queens creating 4-small colonies in the process. The respective colonies grew and did well over late summer but never enough to catch earlier nectar flows. Having worked so hard at grafting I chose not to combine the small colonies into larger ones and sacrifice any of the queens. One colony was used to replace my main hive leaving 3-small populations entering winter. To help those colonies I chose to stack their brood boxes to gain some shared heat over winter. Lacking adequate honey stores for winter I needed to ensure all the colonies had sufficient – food stores. I chose using hard sugar cakes or bricks. I got to work in the workshop and built what I refer to as “feeder frames”. These are frames constructed the size of my brood boxes but enclosed on 3-sides using solid wood and leaving the front-side with an open gap that I filled with a block of wood (a “door”). The “door” or “plug” is removable and given a height just over the thickness of a sugar cake. To feed the colonies it is a simple matter of pulling out the “door-plug” and quickly sliding in a sugar cake. It takes seconds. The sugar cake is positioned directly on top of the frames – in immediate contact with a cluster. Most of the winter the clusters have crawled up and over the sugar cake and hang from the bottom of a quilt used to help control moisture in the hive. Soon I’ll slip each of them a portion of a pollen patty. All this is done without taking apart a hive. There is no disturbance to the colonies with the exception of pushing bees aside when a new sugar cake is inserted. It is a cool system that has worked perfectly all winter. Best is being able to monitor painlessly the amount of sugar that is sitting on top of the clusters. This works so well I have a feeder frame on my main non-stacked hive. So far all the colonies have pulled through winter, but still a few weeks to go. So can not claim 100% success – yet. David’s graphs show well how important it is to keep a watchful eye on what the bees have for late-winter – early-spring food stores. This method makes that very easy. Thanks for the post.

    Reply
    1. David Post author

      Hello Vince

      Sounds like you have a workable system. As with everything beekeeping, there are lots of ways to achieve the right answer … and lots more to not achieve it 😉

      The next 6-8 weeks for us is the critical time (assuming the warm weather arrives as expected) but we first have to survive the next four days of the biggest storm of the winter so far. I’m off to ‘batten down the hatches’ before it all starts.

      Cheers
      David

      Reply
    1. David Post author

      Hello Liz

      I don’t know … I was going to say that you’d have to ask Thomas Seeley but someone has kindly offered me a copy of the 35 year old paper so I’ll read it in full and post a follow-up if it says anything.

      I suspect it was a very small swarm. It looks like there’s a gap in the weight gained per week (bottom panel) at about the same time, so perhaps it was just a couple of pounds of bees that disappeared at a time when there was a very strong nectar flow.

      I should add that I didn’t annotate the swarms. Those were all done by Seeley and Visscher … which reminds me that I should have used blue instead of black arrows to indicate the winter solstice!

      Cheers
      David

      Reply
      1. David Post author

        I’ve now been sent an original of the paper. I’ve looked carefully again at the figure in question. I’m pretty sure there was no overall weight loss obvious with the 1981 swarm because it coincided with a very strong nectar flow (we can make no assumptions about the swarm size as it’s not indicated). The lost bees were compensated by the large increase in nectar stored. The 1981 swarm occurs at the same time as the highest weekly weight gain that year. Presumably, the reduced – but still substantial – gains in the fortnight or so after the 1981 swarm reflect the reduced foraging force.

        An interesting number from the discussion of the paper was the rates of weight loss in December and March. These were 0.42±0.12 vs. 0.84±0.25 kg/week respectively. This fits very well with the figures quoted by Clayton Farrar in the 1930’s. More importantly they emphasise the importance of adding sufficient fondant … 250g won’t even last the 3 days I stated if the colony is losing 0.84±0.25 kg/week. Add 1-2kg and check again in a week or so!

        If your colonies are still upright after Storm Ciara 🙂

        Cheers
        David

        Reply
    1. David Post author

      I’d be pretty sure they don’t discriminate Bridget … if the hive isn’t totally starving (i.e. there are some stores remaining) they still get stuck into the fondant within a very short time of it being added.

      Cheers
      David

      Reply
  3. Karen Alexander

    Thank you for this timely article. I thought I’d share this – I was in the apiary on Wednesday and thought I’d heft the hives. The first I thought was really heavy and the second a bit lighter but still ok. Then as I got home and took my suit off I remembered that they both had their winter straps on. Lol!
    Your advice doesn’t take into account the numpty beekeepers – of which I am surely one!

    Reply
    1. David Post author

      Hello Karen

      I remembered the hive straps after scheduling the article for posting. I’ve made the same mistake several times … Wow, this nuc is really heavy! 🙂

      Cheers
      David

      Reply
    1. David Post author

      Very interesting James

      I don’t usually allow such blatant advertising 😉

      However, I recognise the unit as a digital torque adapter, a variety of which are available in the UK for £40-50. Anyone wanting to make a DIY equivalent would have to learn some basic maths to convert Nm to an indication of weight (though simply determining whether the torque needed to be applied would be sufficient as it’s the change that’s important) and procure a suitable L-shaped bracket.

      Although bees cope well with an OMF they don’t particularly like having the propolis seal cracked open (the jarring as much as the draft, and with a 2mm gap there is likely to be jarring of the brood box) … surely it would be better to have a spacer that fitted between the hive stand and the crossbar at the back of the floor, lifting the entire and intact hive a fraction of an inch? My DIY floors would work well with this if the Varroa tray was removed.

      One of the really big advantages of the luggage scale ‘kludge’ is that it costs about $115 less than the Nectar Detector 😉

      Cheers
      David

      Reply
  4. Jane

    Hello David,
    Thanks for another good post. I’ve been using the luggage scales method through the winter because I’ve got no experience to draw on to judge whether the hive is heavy or light by hefting. I did an internet search on whether the sum of the two sides is really equal to the total, and as far as I could find, the physics did seem to suggest it should be. However, I don’t even get the same reading when I do repeat measurements one after the other, even though I’m trying to only raise the hive slightly and to keep the weigher as vertical as possible. The readings for each side can vary by 1.5kg (though usually by <1kg).
    Rather than spending ages trying to work out what's wrong with my technique, I now just have a quick look through my homemade polycarbonate crown board to see how much fondant is left. For a beginner, that's reassuring, and the recent dramatic increase in consumption wasn't reflected in my measurements.
    I'd be interested to know if you can suggest what I might be doing wrong with the luggage scales.
    (I put two screws into the floor runners on each side and wrapped wire between them to form a loop. I attached a hook to the strap of the scales and stick that through the loop. For things I can lift completely, the scales are consistent within their 100g precision.)
    Best wishes,
    Jane

    Reply
    1. David Post author

      Hello Jane

      I’m pleased you enjoyed the post. The scales are tricky to use because you’re weighing something not at arms length with a straight vertical lift. At least, that’s my experience. With a full hive I also find it difficult to get a steady reading sometimes.

      I’ve yet to find a solution, but have given it some thought. What would help would be some sort of lever arrangement so you could push down on a handle and so pull up on the digital scales. I suspect this would be much easier to get a steady reading and a reproducible weight. There are a variety of solutions online including:

      • Clever lever system but rather too advanced engineering (for me anyway) … and another version of the same thing.
      • One based on a sash clamp that should give fine control.
      • Lever-based (PDF) which is more the sort of thing I was thinking of, though I’d need to consult my basic school physics books on forces to know if the lever was optimal.

      Weighing each side and adding them together is sufficient. The readings on each side may differ if the bees/stores/brood aren’t located centrally … the key thing is whether the sum of the reading differs week after week? Of course the actual weight doesn’t matter really. What matters is whether they are too light. You know what an empty hive feels like … add 1-1.5 kg for the bees and the remainder must be stores and brood.

      I’m also a fan of perspex (polycarbonate) crownboards. One of the pictures above was taken through one of the fondant block being devoured.

      I’ll give the digital scales some more thought … in the meantime it’s always worth very gently hefting the hive on each visit to the apiary. It doesn’t take too long to identify the expected weight.

      Best wishes
      David

      Reply
  5. John Fox

    Quote…
    it’s cold above the crownboard. The bees are less likely to venture up there if it’s chilly and uninviting.

    Surely there are no bees above the crown board ??

    JRF

    Reply
    1. David Post author

      Hi John

      There aren’t in my hives because my crownboards don’t have holes in them 😉

      Even the el cheapo ones.

      However, most commercial crownboards have one or more holes in them. If you place the fondant above the crownboard, allowing the bees to access it through the hole, they are less likely to do so than they are to access the underside of a slab of fondant laying directly on the top bars, immediately above the cluster.

      Cheers
      David

      Reply
  6. John Fox

    David, ref your reply.

    With huge respect, I think you should change the reference to candy above the crown board.
    One would never, ever, leave the hole open. It would be covered with a contact feeder or blocked off. The more so in a candy situation, where by definition, it will be cold.
    Regards. John

    Reply
    1. David Post author

      I wouldn’t leave the hole open (there isn’t one), you wouldn’t … but many would and do. The advice to prop up the crownboard on matchsticks gets ‘aired’ every winter, including in some of the most widely read beekeeping publications. There’s a widely held belief (or unquestioned dogma) that the colony needs ventilating. I’d wager that a significant proportion of colonies went into this winter with the crownboard hole open … I’ve already seen colonies with fondant over the crownboard this winter.

      However, I think the text is clear enough. It’s unlikely to be a disaster and, goodness knows, we’ve got more than enough to worry about at the moment.

      Furthermore, this dialogue will reinforce the point, though the readers of this site are often not those who most need the advice 😉

      Cheers
      David

      Reply
  7. John Fox

    At best the feed hole in the crown board would be covered with a fine gauze allowing ventilation and the option for the bees to propolise over it to regulate ventilation at their discretion. If anyone leaves the hole open the bees don’t stand a chance of keeping warm. Again, with great respect your article implies it is ok to leave it wide open and really should be amended.
    Regards.
    John

    Reply
    1. David Post author

      Hello John

      I don’t think it implies it’s OK to leave it open. Instead it acknowledges the fact that many will have left it open. It’s a reality. I’ve discussed the irrelevance of ventilation previously and shown a picture of a propolised-over splitboard mesh.

      No ventilation required

      I’d prefer beekeepers observe what the bees are telling them and learn from that. Inexperienced beekeepers get easily worried and there are many, many colonies coming through this winter with open holes in the crownboard.

      That doesn’t mean that they might not have overwintered even better with the hole sealed off, but it does reflect the reality of the situation.

      Cheers
      David

      Reply

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