The weather is still warm and the bees continue to work the Himalayan balsam down at the river Nairn. I’ve been harvesting honey and helping a couple of beekeepers prepare their bees for winter as well as tidying the bee shed. I regret that the observation hive has not been occupied for a couple of years and resolve to fill it next year.
Having an observation hive adds another whole dimension to beekeeping, and is a really useful learning tool. We truly learn directly from the bees when we observe them so closely.
It’s also a great way to introduce children to bees in a safe way that builds confidence while satisfying curiosity.
You’re in for a treat this week as Professor Tom Seeley explains how we used this observation hive to find out where the bees were foraging one summer.
Eavesdropping in the apiary: learning where your bees are foraging by reading their dances
Did you know honey bees and human beings are the only two species whose members can tell one another the locations of important resources, such as excellent sources of food, by giving directions on how to find it? We do this whenever we guide friends to an outstanding restaurant by giving them driving directions. Honey bees do this when they direct their hive mates to rich flower patches by performing waggle dances. Thanks to the brilliant investigations of the bees’ dances by the Austrian zoologist Karl von Frisch, we can eavesdrop on the waggle dances of honey bees and learn the locations of the food sources they are advertising.
It is possible to watch a bee perform a waggle dance on a comb that you pick up during a normal hive inspection. In this situation, however, it is very difficult, if not impossible, to take sufficiently precise measurements of the bee’s dance to determine the direction and distance to the flowers that she is advertising. It works much better to watch the dances of bees living inside an observation hive.
My observation hive sits in my office; the bees living in it have access to the outside via tunnel that leads outside. As foragers return from the field, they are steered to one side of the combs by a wooden wedge in the hive. This makes it easy to observe the waggle dances and other actions of the returning foragers.
I use my observation hive mainly as a research tool to investigate the behavior and social life of honey bees. The bees in my hive enjoy the comforts of darkness and insulation when I am not watching them; most of the time, I keep the hive’s glass walls covered with sections of foam insulation.
On 13 September 2016, I visited Scotland for the Scottish Beekeeping Association Autumn Convention that was held in Elgin, and I brought an observation hive to my host Ann Chilcott, so we could put a colony of her bees into it and learn where they were foraging. This hive is shown in Fig. 1.
Besides the observation hive stocked with bees, we needed the following tools for this project: stopwatch, protractor, Ordnance Survey map for the area, calculator, and pencil and paper. We also needed a compass, to determine the sun’s azimuth (compass direction) for the times when we observed the dances. This is easily done; you just imagine drawing a line down from the sun to the horizon, and then see what compass direction this is.
When a forager comes home excited by having had good success collecting nectar or pollen, she climbs onto a comb surface near the entrance and proceeds to run through the figure-of-eight pattern of a waggle dance to inform others where she found the rich forage. In each dance circuit, there is a central, waggle portion with is conspicuous to the other bees, even inside the dark hive, partly because of the waggle movements she makes and partly because she buzzes her wings while she is waggling. The richer the forage source found, the greater the number of dance circuits she performs.
The direction and duration of each waggle run correlate closely with the direction and the distance to the flower patch she has just visited. If the flower patch is located directly in line with the sun’s direction, then the bee indicates this by performing waggle runs that point straight up on the vertical comb. A flower patch located at some angle relative to the sun’s direction is represented by performing waggle runs pointed at this angle relative to the direction of straight up on the comb. You can see an example in Fig. 2 where the flowers lie 40° to the right of the sun’s direction, and the dancing bee’s waggle run is correspondingly tilted at an angle of 40° to the right of vertical. The distance between the hive and flowers is encoded in the duration of the waggle run. The farther the target, the longer the waggle run. You can see in Fig. 1 that a waggle run lasting one second tells the other bees that they need to fly some 500 meters (0.3 miles) before they hit the jackpot, and that a waggle run lasting two seconds indicates they need to fly about 2000 meters (1.2 miles) to find the bonanza.
We made our observations of the bees dancing in the observation hive on a sunny morning – between 10:15 and 11:05. The temperature was around 15°C (ca. 60°F). We read the waggles dances of 11 bees performing strong dances that contained dozens of dance circuits. We chose these bees because their dances lasted long enough for us to get several (average of 6.5) measurements of the waggle run duration with the stopwatch and at least one accurate reading of the waggle run direction (relative to straight up) with the protractor.
For each dancing bee, we determined the direction of the flower patch she was advertising, relative to north, by adding the angle of her waggle runs relative to straight up and the angle of the sun’s azimuth (i.e., sun’s compass direction). For example, one bee’s waggle runs pointed 160° to the right of straight up, and at the time that she was dancing the sun’s azimuth (compass direction) was 156°. Adding these two figures yields 317°, i.e., 43° west of north. Another bee’s dance direction was 220° when the sun’s azimuth was 147°, and adding these two figures yields 367°, which is the same as 7° east of north.
For each bee, we determined the distance of the flower patch she was advertising by referring to the graph in Fig. 2 that shows how waggle-run duration varies with food- source distance. This graph is based on the findings reported by Karl von Frisch in his 1967 book, The Dance Language and Orientation of Bees. The distance indicated by the 11 bees ranged from 500 meters (0.3 miles) to 3600 meters (2.2 miles). The average distance to the flower patches advertised by these bees was 2481 meters (1.5 miles). Pretty far!
Once we knew the direction and distance of the flower patch advertised by each of our 11 bees, we plotted the locations of their patches on the Ordnance Survey map for Nairn and Forres, so we could see where these patches were located relative to familiar landmarks. We summarize our findings in Fig. 3.
We found that the sites fell into four groups:
- Sites along the River Nairn: bees 1, 2, 4, 5, 6, 9, 10. (Note: we suspect that we made a small error in timing the waggle runs of our first bee, and overestimated slightly the distance to the flower patch she was advertising.
- Sites around the Loch of the Clans: bees 3 and 8
- Site around Culcharry Village: bee 7
- Site near Tomluncart Farm: bee 11
These results are supported by what we found when we explored the locations indicated by the bees’ dances. First, we looked for flowers and bees along the banks of the River Nairn between Howford and Little Kildrummie, and there we found dozens of stands of Himalayan Balsam (Impatiens glandulifera) being visited by honey bees bearing silvery white stripes of pollen on the thorax (see Fig. 4). This matched what we had noticed when we were taking the measurements of the dancing bees: most, but not all had a silvery white stripe of pollen down the center of the dorsal surface of the thorax. Also, some bore pollen loads that were cream colored. Both things are typical of bees foraging at Himalayan Balsam.
One week later, on 20 September 2016, Ann and Linton explored the areas around the Loch of the Clans and the Alton Burn (stream) which drains from the loch, and there they found Marsh Woundwort (Stachys palustris) being visited by bumble bees. No honey bees, however, were observed on these flowers that day. Probably, the bee that had been foraging there had switched to a richer site somewhere else.
A month later, in Culcharry Village, Ann and Linton found a field with tall ragwort (Senecio jacobaea) plants still in bloom (Fig. 5). This plant is unpopular with humans because it is toxic to horses, but is beloved by honey bees because its bright yellow flowers offer profuse nectar and pollen.
Another search was made around Tomluncart Farm for flowers that were being visited by honey bees, but found were none. It is possible that our measurements of waggle run duration for Bee 11 were slightly mistaken, so that we underestimated the distance to the flower patch that Bee 11 was advertising. If so, then it is likely that this bee was advertising flowers around the Loch of the Clans, which is in the same direction as Tomluncart but ca. 1000 m further from the hive.
So, overall, what did we learn about the foraging activity of our observation hive colony by noting and deciphering some of the waggle dances performed by its foragers?
- Many of this colony’s foragers were exploiting Himalayan Balsam flowers along a large stretch of the banks of the River Nairn, from near Rosefield in the west to near Howford in the east.
- Some of the colony’s foragers were exploiting at least two other sites with flowers besides those dotting the banks of the River Nairn: patches of Marsh Woundwort in or around the Loch of the Clans and a pasture containing Ragwort in the village of Culcharry.
- The main source of forage at the time of our data collection was Himalayan Balsam.
- The bees were travelling impressive distances to collect their forage: nearly all were going at least 2 km (1.2 miles), and on average they were flying 2.5 km (1.5 miles) to reach their food sources. We saw no sign of foragers travelling more than 3.6 km (2.2 miles) from their hive.
- The colony’s foragers were not spread uniformly over the countryside around their hive, but instead were focused on a few distinct, and widely spaced, places that had (presumably) the most profitable flowers.
I hope that this report on bees sharing information about rich food sources kindles, or perhaps rekindles, your interest in this astounding aspect of bee behaviour. For some it may be a complete revelation that has got you reaching for the books to learn more. However you have reacted, I hope that you feel inspired to build an observation hive, install a colony in it, and try this bit of sleuthing for yourselves.