Winter Feeding

© BBKA News No 216 - August 2013

We are getting to that time of the year when we should begin preparing our colonies for winter. Honey bees collect nectar in the warm months and put it into long-term storage as honey in
order to have stores for the winter. These stores are used both to survive on, as food, and as fuel for keeping the colony warm as it clusters to pass the cold winter months. Bees eat the diluted honey and use their powerful wing muscles to generate heat thus converting the sugars into energy and keeping the winter cluster warm. It is imperative therefore that we, as beekeepers managing colonies for our own use, ensure that each colony has sufficient honey to last until next spring when the bees can begin to collect fresh nectar again.

What is considered to be ‘enough’ honey stores in our northern temperate climate?

As in all things to do with bees, the answer is, it depends. Some races of bees are frugal but others eat lots in the winter. For the average colony, around 20 kg (45 lbs) of stores are required
although larger colonies of more prolific races such as the Italian bee,
Apis mellifera ligustica, may need more and our native black bee, Apis mellifera mellifera, will consume less. Go by how much space the colony needs during the summer; take 20Kg (45 lbs) of stores as an average requirement for a colony which is comfortable with the queen laying in a single brood box, but allow 25 kg (55 lbs) if the colony is on brood and a half.

To assess the amount of stores in a colony going into winter, it is useful to know that a British Standard brood frame holds just over 2 kg or around 5 lbs, so nine full frames of honey will be needed. For a Langstroth, this comes out at around 3 kg per frame, so assess accordingly. It now depends mainly on the beekeeper. If it has been a bad year for the honey crop and a colony does not have sufficient stores according to assessment, or if the beekeeper takes as much honey as possible leaving insufficient for the bees, then they must be given a supplement. Of course commercial honey farmers have to maximise their yields in order to make a living, but for the amateur beekeeper, consider leaving a super of the colony’s own honey, which one feels instinctively must be best. Remove the queen excluder until spring so that the cluster can
move into the super easily as it will not leave the queen behind. There is a view that putting the super below the brood box is the best way; both options have their merits.

The substitute or top-up that we give our bees is sugar syrup. Feeding honey should be avoided as there is a risk of spreading disease and the odour of honey increases the likelihood of robbing. Syrup is odourless. Ready prepared feed is available commercially and very convenient for bee farmers, but most of us make up our own feed from white granulated sugar, which is pure sucrose and
one of the three main component sugars of nectar. Never use raw or brown sugar. This may sound counter-intuitive when we consider that these less processed (usually) sugars may be thought to be more natural than the white stuff, but the impurities in it are harmful to bees. Icing sugar often contains additives as well as being more expensive than granulated sugar.

Before going into the detail of how to make up the syrup some issues need to be addressed. The strength of syrup is often quoted as ‘light syrup, spring feed, 1:1’ or ‘heavy syrup, winter feed, 2:1’ which without units is meaningless. In the days when we in the UK used mainly Imperial measures, these proportions meant respectively 1 lb of sugar to 1 pint of water, and 2 lbs to 1 pint.
However, now that we have moved to metric measures, we need to understand exactly what these figures mean as they do not translate to 1 kg sugar in 1 litre of water, etc. So, here follows the maths.

Sugar should be fed as syrup expressed as a percentage, and for winter feed this is a little over 60%. Research at Rothamsted has shown that the optimum concentration for bees to process syrup fastest and store most is 60%, with greater concentrations becoming progressively less interesting to bees. Take our 2 lb of sugar to a pint of water as an example:

2 lb of sugar weighs 2 x 16 ounces i.e. 32 oz.
1 pint of water is 20 fluid oz.
The total weight of this mixture is then 32 + 20 = 52 oz.
The percentage of sugar it contains is 32/52 X 100% = 61.5%.

Since 1 litre of water weighs 1 kg, if we metricate our ‘2:1’
example for 2 kg sugar dissolved in 1 litre of water we get:
Total weight of mixture = 2 +1 =3 kg.
The percentage of sugar it contains is 2/3 X 100% = 66.6%.

However, for 2 kg sugar dissolved in 1.25 litres of water:
Total weight of mixture = 2 +1.25 =3.25 kg.
The percentage of sugar it contains is 2/3.25 X 100% = 61.5%

Halve these numbers and you get 1 kg sugar in 625 ml of water. Although here we are not concerned with light syrup, similar calculations will give 1 lb sugar in 1 pint of water as 44% but 1 kg sugar in 1 litre of water is 50%. To make up 44% in metric measures,
we need 1 kg sugar in 1.25 litres of water (1/2.25X100=44%). Therefore do be careful when quoting 1:1 or 2:1!

Now to calculate the amount of syrup to offer. In approximate terms, 10 kg of sugar made into heavy syrup gives a volume of about 25 litres and weighs about 16 kg, providing 15kg of stores and being equivalent to 12 kg of honey (16 lbs of sugar made into heavy syrup gives about 23–24 lbs of stores and is equivalent to 20 lbs of honey). To make up the syrup, mix the required amount of sugar with hot water and mix as quickly as possible until all the sugar has dissolved to give a clear solution, which has a pale cream tint. Do not boil the mixture in an attempt to dissolve it all because this can break down the sugar and produce the organic molecule hydroxymethylfurfural (HMF) which is toxic to bees. Cool it down before adding to the feeder. At this strength the syrup can be stored, but keeps best if a little thymol is dissolved in surgical spirit and mixed with the sugar solution.

Thymol crystals are hardly soluble in water but dissolve easily in alcohol, so according to a recipe adapted from Rob Manley’s original:

  • Careful handling of thymol crystals is essential, as they are harmful to the skin.
  • Dissolve 30 g thymol in 150 ml surgical spirit (1 tsp in 5 floz) to make a stock solution.
  • Add 5 ml stock solution to 13.5 litres syrup (1 tsp to 3 gallons).

When should we give our colonies this syrup in order to supplement their winter stores?

The basic principle is: feed early enough so that the bees can invert the sucrose to fructose and glucose, evaporate the water content to reduce it to around 18% for storage and seal it over as they would for nectar. This is before the weather turns cold, so around the end of August or the first week in September when the colony is still well populated. If this is not achieved then the partially processed syrup might ferment and bees will suffer from dysentery. They do not defecate in the hive under normal circumstances and the rectum of a bee is capable of expansion, so in winter they can retain waste for a long time. However, if forced to defecate in the hive the colony’s hygiene is compromised, and if any nosema is present it will be spread rapidly as the house bees attempt to clean up the infected faeces.

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Feed too early, though, and they will convert the syrup into brood. As a guide then, after the supers have been extracted and given back to the hives to be cleaned up remove them and make an assessment of requirements. Then feed using a rapid feeder, such as the Miller or Ashforth, in order that the bees can process it quickly. See Paul Smith’s article on page 13 for a good account of the various types of feeders that could be used.

As always, we feed bees in the evening, never during the day. The reason for this is that bees can tell each other where a new source of food is to be found using the famous waggle dance.

However, when the distance to the source is under 50 metres (some say 100m) they are unable to specify exactly where the source is and so bees go rushing around outside the hive, searching for food and will enter other hives, find their stores and a big robbing situation results!
It does not ferment and may be placed in a plastic bag over a hole in the crownboard without disturbing the colony. Pierce a few holes in the bag and bees will come up to take it when the temperature allows them. They need water to be able to use solid food and this is available as condensation within the hive. However, in an emergency, spray the bees lightly with 44% syrup and give them a frame with the cells filled with syrup.

In order to assess the amount of stores there is in a colony going into winter, it is useful to know that a British Standard brood frame holds just over 2 kg or around 5 lbs, so nine full frames of honey will be needed. For a Langstroth, this comes out at around 3 kg per frame, so assess accordingly.
Bridget Beattie, NDB

In nature colonies store food for the winter. If we take the honey from our managed colonies which they have stored for winter survival we must ensure that we leave them enough to last until foraging begins again in spring or provide them with a substitute to see them through. Without it, they will starve. They also need pollen but they usually store enough to last and we do not normally take this from them.

The National Bee Unit has some excellent advisory leaflets on their website BeeBase at index.cfm including more information about feeding bees. Do not forget to sign up to BeeBase while you are there as it is a great resource for beekeepers.

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If the colony is fed when the bees are no longer foraging for that day, they will discover their food source within their hive by the next morning and mayhem will be avoided. The entrances should be reduced by inserting the entrance block to help each colony to defend itself more readily from robbers. All colonies in the apiary should be fed at the same time so that all are in the same state of awareness of the food source, which also helps to avoid robbing.

It is very important that no syrup is spilled; if it is it must be cleaned up immediately. Do not leave syrup open to bees in the apiary. Once begun, robbing is very hard to stop. If all the syrup is not taken down by the time the cold weather arrives, remove the remains to prevent it fermenting and monitor the hive by hefting, as described below.

We may be faced with a dilemma because this is also the time when we treat colonies against varroa and when preparations involving essential oils are used robbing may occur more easily. Follow the directions on the treatment packet.

Topping up the colony’s stores for winter should ensure that they will not starve. Sometimes, however, during a prolonged cold snap the cluster does lose contact with its food and isolation
starvation takes place, but that is another story.

It is a good idea to practise what is called ‘hefting’ a hive in order to estimate its weight and thereby its possible stores in winter. This simply means getting into the habit of lifting the back edge of the hive off the stand before or after an inspection and getting a feel for its weight, coupled with the visual assessment of weight by observing the amount of capped stores in the frames. Then in winter when the hive should not be opened, we can get an idea of whether it is feeling a bit lighter than it should, perhaps indicating that the stores are running short.

This is particularly important during the late winter/early spring period when the colony may have used up its food and is in danger of starving. When unsure use candy, which is available from beekeeping suppliers or there are recipes in many beekeeping books.