We are pleased to give an update on the free living honey bees project at Pertwood Organic Farm. The project was set up to provide more options for honey bees to nest around the farm and thus hopefully increase the number of bees. This increase would contribute to the pollination of flowers as part of the organic system, including special mixes of flowers which fix fertilising nitrogen into the soil, provide nutrients to the grazing animals and well ... just look great along the side of the A350!
Prior to this project the spaces that bees could use for nests were limited to chimney stacks and even underground concrete water meter chambers: all unsuitable. The natural homes of bees - hollows in trees - had all but gone. Whilst the farm is quickly increasing the area of wooded habitat, it will take 100's of years for these trees to age and become suitable for honey bees. So, while we wait, we are providing some alternative accommodation.
For those of you who have been following this project you will know that in 2016 we created a cavity inside an ash tree which was populated by a wild colony of bees within two days of its construction (see video). Additional bee nests (think of a bird box, but much larger and made from really thick wood), have been dotted around the farm to provide nest sites for swarms from the original ash tree colony. This article follows an October 2020 visit where we checked up on the progress of all the nesting locations to see how the bees are doing. The weather was terrible, and no bees in their right mind would be out and about. But we had a special technique to help us determine if the nests were occupied when the bees were not flying:
A long tube was put up to the entrance and gently blown into. In the populated hives, the bees buzzed back as they felt the air movement and CO2. All it took was to put an ear to the tube and we heard this unmistakable buzz of life.
Using the tube we were able to determine that the log hive in the picture and another tree box hive nearby were populated with honey bees. Sadly, a hive further up the field which used to have a strong colony was silent.
From the original ash tree hive in 2016 there are now two honey bee colonies ... that we know of. It may not seem a big change, but this project has always been delicate; we started from just one nest and have resisted the urge to artificially boost nature. The intention was always to provide agency to the bees rather than push expansion artificially. We take heart that the project has expanded, but the small increase reflects how difficult it can be to recover natural systems when so much of the original habitat that supported them has been lost. The original tree hive inside the ash tree is now empty, yet surprisingly has become of special interest. Nests typically last 3-6 years, although we know of some that have lasted for decades. But once a nest becomes unoccupied what happens in this mysterious chamber, and when can it be recolonised? These questions have been little researched. We know that in managed hives beekeepers typically clean them once a colony dies; indeed, it is considered good practice to thoroughly clean a hive with a blow torch to prevent disease. Wild colonies on the other hand are never cleaned out, and yet several studies show that they have higher resistance to diseases and their nests do not create disease hotspots. So, what happens in the wild? Are nests cleaned, and if so, how?
We inspected the empty ash tree hive last year just after it was abandoned, and although there was interest, other colonies decided not to swarm into it.
In a natural nest, the comb and nest walls are normally covered in sticky red propolis, a resin based material created by the bees which is anti-microbial and anti-fungal. The propolis creates a nest atmosphere but only in nests which have high thermal inertia and insulation e.g. a tree. The atmosphere protects the bees from pathogens and also stabilises the tree cavity. If the bees quickly reoccupy the nest with a new swarm, all is fine to continue where the previous colony left off. But if there is a gap, nature breaks down old comb before the bees start again.
We opened the ash hive again on this visit to see what the comb was like after a year and a half.
The picture above of the same nest shows that almost all of the comb has been eaten by wax moth and the detritus is being processed further by earth worms (4m up a tree!) and other micro organisms. This slow but very thorough breakdown is thought to be one of the mechanisms which prevents disease replication in honey bee colonies. Literally everything, including the propolis, is consumed many times over. With less than a quarter of the comb remaining, the rest of the nest is empty and will likely be ready for bees again in the spring.
This breakdown is slow and looks a mess but it is actually all part of a symbiotic cycle between the bees, wax moths and other creatures/bacteria. So, one colony died, but not before establishing two daughter colonies; besides, the nest now teems with many other organisms. As we went around the farm checking the various nest boxes we found this oddity.
Clearly, a swarm found this nest and spent some weeks outside, as shown by the comb on the exterior, but for some reason they did not go inside. In an effort to find out what happened, we looked closely at the comb.
Firstly, we noticed there were a few scattered raised open cells in the centre of the comb which, due to their shape, must have once had male drone larvae in them. The fact that they were randomly distributed, clustered in the centre and not at the edge, and smaller than normal drone cells suggests they were laid by sterile worker bees. Female worker bees lay unfertilised eggs (that hatch as drones) after about 30 days of being without a queen due to the absence of queen pheromones.
Looking further at the comb, we saw no signs of extensive honey gathering. Had honey been stored the comb it would have been raided by stronger colonies as the nest failed, and the edges of the comb holding capped honey would have been ripped open and serrated by the raiding bees. In other words these bees lacked purpose to gather honey.
The very existence of the comb showed that the scout bees looking for new nests thought this location was good, but the bees did not enter the hive - again indicating the arriving swarm lacked purpose.
We also noted that the comb was pure white. If a queen had been laying eggs, we would have seen a darker yellow at the centre of the nest as the bees would have been constantly feeding the developing bees with pollen, staining the comb. The lack of colour suggests the bees lacked young bees to feed.
From these clues, we speculated that a reasonable sized swarm attempted to enter, but the queen likely never made it with them into the nest. Possibly she was an old queen and unable to fly, or she was lost on the way. Perhaps they waited for the queen, staying under hive and slowly diminishing for over a month until eventually they all died or dispersed to the two nearby colonies. We will never know for sure, however we are reminded that the act of reproduction is an uncertain event for bees.
In summary, then, we can say that the original ash tree hive, from which many swarms issued, is now in a state of cleansing and renewal. Two swarms have made it through their first season, with a third sadly lost, and yet another large swarm that disappeared into the surrounding countryside. The project is revealing the many connections between honey bees and other organisms that co-exist with the bees. This project is one of many similar projects that are being created for free living bees around the world. You can find more projects here. Looking ahead at Pertwood Farm, we now have two young colonies which will be in their second season, just perfect for swarming in 2021. We hope then that we will have 3-4 colonies, but it's all up to the bees and nature where this project goes. These colonies are delicate threads in a tapestry of natural relationships. Nature transitions away from relationships that do not work and flourishes where the relationships between organisms and the environment are mutually supportive. At Pertwood we want to listen to bees and seek ways to support them. Once the bees thrive in all areas of the farm we will know whether we've listened (and acted) with true understanding.