Can Wild Bees Survive in Our Forests?

I spent a glorious few days last week helping teach a dedicated group of beekeepers how to make 5 tree hives (slots cut into trees) and 8 log hives for the Steigerwald forest in Bavaria. This is a very progressive forest where 1,000 ha of the 17,000 ha forest are dedicated to bio-diverse forestry.

Look carefully and you will see the tree hive (click for larger)

In the bio-diverse forest 10% of trees which have holes, bark damage, fungus or of significant size are marked as habitat trees and are protected. Trees which have fallen down are allowed to rot. In the past these trees would have been culled and removed creating a sterile forest. The average size of tree in the managed forests are typically 40-50 cm girth, whereas trees suitable for bees need to be 70-80cm with at least a 40 ltr cavity. Little wonder the head forester only heard of 3 wild tree bee hives in his many years of forestry.

Steigerwald foresters with the help of European Forest Institute/EFICENT organised the tree hive making course to kick start the re-population of the forest with bees. It's going to take many years for the size and the condition of the trees to be right, but the introduction of tree hives (beute - bort) and the craft of the tree hive keeper (zeidler, bortnik) marks a great start.

Will the bees survive? is a good question. In the Baskir tree hives found in the southern Urals, about 30% of the 700 hives are naturally occupied. In very good years all will fill and in very poor years the number can drop to 10%. However the Bashkir bees, despite harsh winters, have a tremendous advantage; the forests in the Urals are home to 1/3 of the European linden trees - a fantastic source of nectar for the bees. Typically the natural life of a Bashkir hive is 8 years, and this figure resonates with some of the established wild hives I have known in the UK. Failed hives rendered down by the wax moth are particular attractive to swarms.

Results in the recently establish 50 Polish tree hives have not been so good with 60-70% failure in the first 6 years at the first two locations. Tom Seeley, the well known bee researcher observed that 75% of swarms fail in their first year which probably accounts for the high start-up losses. I often call these swarms "pioneering swarms" as they leave behind markers and structures for other swarms to find quickly and use. I think the Polish figures will improve as the program expands. 

Wild bees need:

• A critical mass of bees to replace losses and pioneer

• Hives high in tree cavities where the humidity is lower

• Sources of diverse pesticide free forage from spring to autumn

The Bashkir and the Poles (who attended the Steigerwald course) do not treat their bees with pesticides or antibiotics. Where bees naturally distribute the incidence of nosema and foul brood diseases are much lower than in hives kept by beekeepers. This is backed by several research studies  (Mark Goodwin's (NZ), Allen L. Szalanski (USA)). The foul brood curse affecting bees is often called the beekeepers disease for good reason. So I think this adds an additional but difficult requirement:

• Enough suitable homes to allow a natural spread of 1 hive per 1km2

The Bashkir actually provide 3 tree hives per km2.

The next tree hive making course will be in Switzerland July  2015. I hope we can also run a UK course in 2015, but this will depend on finding a suitable forest host.

I will post a few more articles from the Bavarian  zeidler fest in the following weeks.