4 minute read

Weighing top-bar hives

Marieke Mutsaers (1) and Christopher Campion (2)

(1) Trichilia ABC, Noordermeerweg 65 cd, 8313 PX Rutten, The Netherlands

(2) Integrated Tamale Fruit Company, Tamale, Ghana

A beekeeper can assess the condition of a colony from outside the hive. The behaviour of the bees, and the presence of drones, indicate whether the season is going up or down. The presence of a ‘beard’ of bees indicates that the hive is full. With experience, the beekeeper knows exactly the seasons in the local area. However, the number of combs within the colony at any time can be known only by internal inspection of the colony. There is a way to gain objective data without opening the hive, and this is to weigh it. This is an especially good option for top-bar hives, as they contain only natural combs. Subtraction of the empty weight of the hive gives the weight of the colony - that is combs and bees. A very good and cheap design for weighing hives is given by Hillyard (1968). It can be made with a fruit carton, which can hold about 100 kg in weight. Lay the scale on top of it, upside down, and mark the place where the dial is, then cut a hole in the carton. Next a semicircle is cut at the side, so that the scale can be read using a mirror placed underneath the carton. A similar design is then made of wood. Abdallah Ibrahim, carpenter for the Integrated Tamale Fruit Company, made this design as well as the hives.

Reading the weight of a hive
PHOTOS © MARIEKE MUTSAERS

To weigh hives in the apiary, three people are needed: two to hold and lift the hive, and one person to shift the scale underneath and let it stand properly. The weight can then be read. Two readings must be taken to be sure. The operators have to get used to the mirror reading, while the hive is standing free. The first reading is noted down and then the second before the hive can be lifted again to remove the scale.

The hives are numbered. The empty weight of the hive is obtained beforehand. If hives are already colonised it can be obtained later if the colony absconds or is transferred into another hive. The top-bars are laid in place, the lid put on and the weight is recorded in a table with other data, including the name of the beekeeper and where the apiary is located.

A full registration of hives with exact data on the colonies comes into the picture. The hive does not need to be opened to have an idea how full it is. I found that the maximum weight of bees and combs in kg (WBC) is about half the volume in litres. This is at the peak of the honey flow when the colony has its maximum weight. For example, if the volume of the top-bar hive is about 80 litres, the maximum weight is 40 kg (WBC). A hive of 50 litres contains a maximum of 25 kg, and one of 100 litres a maximum of 50 kg. Seasonal management of colonies can now be based on objective data. If weighing is done monthly, a graph can be made to give a good insight into colony development during all seasons (see next page). A good insight into colony development: the graph shows seasonal weight of a large top-bar hive in Africa, northern hemisphere.

The scale is reflected in the mirror
Lifting the hive and moving the scales

Hillyard (1968) put a periscope (double mirror) at the back to read the weight easily, and put a hive permanently on the scale. However, I found that everyone soon learns to read the weights easily in the mirror, and African bees do not like the hive wobbling on the scale and can become defensive. Crane (1990) described the weighing of hives with this scale but did not subtract the empty weight of the hives, just registered the increase and decrease of weight. With top-bar hives this is possible and it gives us a better idea of the status of the colony.

WBC    =     weight of bees and combs

25 kg dotted line      =      maximum weight of bees and comb in a small hive (50 litres)

50 kg dotted line     =      maximum weight of bees and comb in a large hive (100 litres)

References

CRANE, E. (1990) Bees and beekeeping: science, practice and world resources. Heinemann, Oxford, UK. pp 165-166.

HILLYARD, T.N. (1968) Simple hive scales. Bee World 49 (3): 102-103.

MUTSAERS, M. (2008) Visit Report, Integrated Tamale Fruit Company. Unpublished report.