Appropriate design of top bar hives
by Liana A M Hassan, Director, Njiro Wildlife Research Centre, Tanzania
IN AFRICA BEEKEEPING IS traditional, economic activity. Honey is valued, not only as nutritious food, but also as a product with cultural values. Traditional hives are characterised by fixed combs which do not allow harvesting of honey without damaging the brood combs.
Movable-comb frame hives have been introduced in various beekeeping development programmes in Africa with little or no success. In some cases careless importation of this technology has produced disappointing results. To eliminate the expense involved in producing frames for hives, many different designs of top-bar hives have been developed.
The problem in using top-bars in place of complete frames is that the bees may attach the combs to the side walls making comb removal difficult. According to Kigatiira (1974), the degree of comb attachment was significantly higher in top-bar hives with vertical side walls than in those with sloping side walls. Similar results were noted by Free and Williams (1981), and Budathoki and Free (1986). However, in Botswana, Kenya and Tanzania it has been reported that there was little or no comb attachment to vertical side walls of top-bar hives (Ntenga, 1972; Ntenga and Chandler, 1972; Clauss, 1984).
In view of these contradicting observations Budathoki and Free (1986) recommended more experiments in the areas where top-bar hives are used. The comb attachment to side walls of top-bar hives has now been investigated in series of experiments conducted by Njiro Wildlife Research Centre in collaboration with beekeepers in northern Tanzania (1991-1997).
Five designs of top-bar hives, all the same width at the top (48.6 cm), height (25.7 cm) and length (89.2 cm), were constructed using seasoned timber 1.9 cm thick. The five designs had side walls sloping inwards at 0°, 5°, 10°, 20° and 30° from the vertical (see Figure 1*). Each design held 27 top-bars each 3.2 cm wide which fitted tightly to form closed top for the. hive. In total thirty top-bar hives were stocked with honeybee colonies previously established in frame hives. The stocked hives were placed on bench stands in well maintained apiary at Njiro Wildlife Research Centre. The number of combs, and the numbers of combs attached to the side walls of the experimental hives were recorded in series of five inspections.
Results from the preliminary experiments stimulated detailed experiments using only two designs (0° and 10°), which were considered the best. Twenty colonies were established in hives with sloping side walls of 0° and 10° only. The hives were either hung from wires or placed on wooden hive stands. The length from the bottom of the top-bars to the first point of attachment (A) and length of attachment (B) were measured (see Figure 2*). Only data from combs 80-100% of full size were considered in analysis.
Building hives with 20° or 30° wall slope requires skilled carpenter and the use of electrically powered machines. A hive with 10° wall slope can easily be made by carpenter using small hand plane.
*Where reference to images or figures is made, please see the original journal article
Hives with sloping walls are preferable for the following additional reasons:
- Less timber is consumed in hive making.
- A hive box with sloping slides is stronger than rectangular box.
- The hive walls are subject to less solar radiation during the day.
- The sloping hive walls offer better protection against heavy rainfall. The inside corners at the base of the hive are less pronounced. This makes them less accommodating to wax moth larvae and other pests that breed in the debris that collects there.
a) Preliminary experiments using five designs of hives
There was noticeable reduction in the degree of comb attachment from vertical walls (0°) to slight slope (5° or 10°) and an increase in the degree of attachment for greater slopes (20° and 30°).
b) Detailed observations based on the two designs of hive
The total number of combs built in the 20 hives was 445. The average number of full combs per hive during nectar flow was 16, range: 10-22 combs.
Comb attachment on the side walls was more pronounced in the vertical hive walls (0°) than on slightly sloping side walls (10°) as shown in Table 2*. Analysis by Chi-square distribution indicated that there was significant association between the slope of the side walls of the hives and comb attachment (chi-square 3.860, df 1, P<0.05).
*Please see the original journal article to see Table 1. Number of combs, and number and percentage of combs attached to side walls in top-bar hives with side walls sloping at different angles. Averages over five inspections and Table 2. Comb attachment to the vertical (0°) and sloping (10°) side walls of top-bar hives.
Discussion and Conclusions
In the preliminary experiments the designs having 20° and 30° indicated high degree of comb attachment and therefore in the subsequent experiments they were left out. These designs were more difficult to construct using manual, hand tools than the vertical one.
This observation was also reported by Ntenga (1972), Ntenga and Chandler (1972), Clauss (1984) and in personal communication with Clauss (1992) and Paterson (1993).
During the subs experiments it was therefore important to critically answer the question: “Is sloping wall necessary”. The results obtained from the 497 combs suggested that slight slope of the side wall is necessary in reducing the degree of comb attachment.
There was no remarkable comb attachment to the walls of hives which were hung from wires. During inspection the longest comb attachment of 120 mm did not present any difficulty in removing the combs.
Our observations and those of beekeepers who used the experimental hives confirm that the degree of comb attachment to pronounced sloping side walls is higher than in hives with slight sloping side walls. But the length of the attachment is too small to present any practical problem during hive inspections. However, the hive designs which have side walls sloping at 20° and above are more difficult to construct than those of vertical or just slight slope (10°). Additionally more timber and space are wasted when constructing the floor boards of the trapezoid hives.
In one hive only, 22 combs were built but the average number of combs and mode were 16 and 15 respectively. Consequently the appropriate volume of top-bar hives (with 10° slope) at higher altitudes in northern Tanzania would be hive accommodating 20 top-bars only. Such hive should be big enough in a good honey flow season.
In areas where the hives have to be hung from wires instead of sitting on bench stands, care must be taken to ensure that the hives are horizontal. Whether the hives are suspended on wires or placed on bench stands any slight tilting to either side may cause cross combs or side wall attachment.
Njiro Wildlife Research Centre and Bees for Development are co-operating on the project “Sustainable Beekeeping for Africa” funded by the United Kingdom DFID. Thanks are also due to Börje Svensson who assisted with this work.
BUDATHOKI,K; FREE,J B (1986) Comb support and attachment within transitional bee hives. Journal of Apicultural Research 25: 87-99.
CLAUSS,B (1984) Bees and Beekeeping in Botswana. Beekeeping Division, Botswana.
CLAUSS,B (1992) Personal communication. Port of Spain, Trinidad.
FREE, J B; WILLIAMS,| (1981}. The attachment of honeybee comb to sloping hive sides and side-bars of frames. Journal of Apicultural Research 20: 239-242.
KIGATIIRA,K I (1974) Hive designs for beekeeping in Kenya. Proceedings of Entomological Society of Ontario 105: 118-128.
NTENGA,G (1972) Hive development in Tanzania. American Bee Journal. 112: 20-21.
NTENGA,G; CHANDLER,T (1972) The Tanzania bee hive. Ministry of Natural Resources and Tourism, Dar es Salaam, Tanzania.
PATERSON, P (1993) Personal communication, Arusha, Tanzania