30 : Hive Scales Figure 2. Colony weight (kg) over a period of Robinia pseudoacacia nectar flow
Figure 3. Colony weight (kg) as a measure of a colony’s metabolism (strong colony – green line, small colony – blue line) just before the onset of strong nectar flow
data, greatly enhances the overall understanding of a colony’s dynamics. In Figure 4, the weight graph is overlaid with that for acoustic-based flight and the fanning profile, showing clearly that increase in flight activity corresponds to increase in weight. Based on this correlation, it is possible to assess the foraging efficiency of the colony. Not all foraging flights are equally productive, often because of environmental factors such as the weather, but pollution has also been shown to decrease the honey bee’s ability to recognise floral cues (Girling, et al). Similarly, an increase in fanning activity correlates to decrease in weight as moisture is evaporated from fresh nectar.
Management Tool As our hive scales have been
Figure 4. Weight in relation to flight and fanning activity Figure 5. Weight decrease and flight activity during a robbing episode
swarm calculated, 2.6 kg in this case.
During periods of dearth, when no forage is available, consumption of stores reflects the energy required to maintain the colony (Figure 3). The
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stronger the colony, the higher are its energy requirements. This is particularly relevant during wet springs when weather conditions impede foraging and/or nectar production by the plants and a strong healthy
colony can perish in a short time due to starvation. Weight alone offers a wealth of information about the colony. However, the ability to combine it with other measurements, such as acoustics and weather
more widely used in beekeepers' apiaries, it became clear that the information obtained was very valuable in terms of apiary management as it can save time, work load and unnecessary disturbance to bees. This is how the e-mail and SMS alerts came into existence. Initially, the most obvious alert to make available was maximum and minimum weight. Knowing when to add a honey super is worth gold to honey producers. Most of us can relate to opening the beehive and finding the crownboard stuck down by white brace comb, at which point you realise that if only you had supered a few days earlier, the bees may have filled half a super with nectar. Imagine then looking down a line of 100 hives.
Minimum weight information alerts the beekeeper that feeding is required. Colonies are most vulnerable to starvation as they come out of the winter,
April 2015 Vol 97 No 4
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