ONBG meeting, July 2021 – Blenheim wild bees

We were priviliged and excited to have the opportunity for a behind-the-scenes tour of wild bee colonies at Blenheim Palace led by Filipe Salbany, an internationally experienced bee expert who emits a real contagious joy and enthusiasm. He has 50 years’ experience with bees on 3 continents and many hive types, thus a much broader perspective than most beekeepers.

Bees living in a natural cavity in an old oak tree

Blenheim Palace is a vast estate, 2500 ha, and due to historical quirks it contains Europe’s largest ancient oak forest and many other huge old trees – exactly what bees evolved to live in. This was a fantastic opportunity to learn more about how bees live in their natural setting. Most of us have seen a few wild colonies, in roofs and the odd tree, but never so many at once, and not in such an extensive landscape.

We walked round for 3-4 hours, covering a small fraction of the grounds. The layout was essentially frozen in time about 300 years ago, and the sheer size of the grounds and this consistency in forage patterns has meant that the wild bee population there has managed to remain pretty much isolated and exceptionally adapted to the local environment.

Filipe describes a beelining technique: dark backgrounds, like the lake make it easier to spot flying bees.

There was some architecture stuff too, herds of tourists (much of the time we were in the wilder areas more distant from them) and various surreal encounters when our paths intersected some art installations.

The Blenheim Bees in Trees Project

Filipe got involved with the Estate through a chance after-dinner conversation. Someone mentioned there was only one wild bee nest at Blenheim. “Oh, I bet I could find more” he said, having a lot of experience tracking down nests (beelining) in Africa. He found several on his first visit, everyone got very interested, and the estate gave him access and support from the Forestry department. The Estate has realised it has a possibly unique resource here which is worth protecting, promoting and researching. So far he’s found 35 nests in under a year, and there are large areas he has not checked yet. Interest was further piqued when a swarm flew over the Palace and settled on a wall while the Duke was holding a formal dinner.

Inside the nests

Photo (c) Filipe Salbany 2021

There was a lot of walking and talking, as Filipe described how he found nests and what’s in them. Did I mention he’s an accomplished climber? Some of these nests are 20 metres up. Even with safety ropes and helpful foresters, they are pretty tricky to reach. Once up he is sometimes able to see what’s inside using his mobile phone as a camera – stick your arm in, point the phone around, remove, examine footage and repeat. He wears no protective gear, not even a veil; his arm is quite scratched where it’s got a bit stuck in the nest holes at times – if he wore gloves they would tend to wrinkle up and jam as he pulled his hand out. He is hoping to get a proper endoscope before he drops his phone down a tree cavity. “How often do you get stung by these wild bees?” we asked. Answer: never.

The eco-floor debate: Some people put sawdust or leaves on the floor of hives, believing this mimics natural nests. I’ve always been sceptical of this. Filipe told us these nest floors are kept pretty clean, especially where the combs extend close to the bottom of the cavity. But, he does see an amazing variety of fungi and invertebrates on the floors. I asked him to expand on this as his statements seemed contradictory. He said yes, there are a lot of things living there; but the bees rapidly clean up mess so there are only a few flakes of wax and stuff down there at any one time. The only exception was where an old nest had died and disintegrated into the base of the cavity, then the cavity was recolonised by another swarm and the new tenants had not yet cleaned it up.

Inside an oak nest, looking up at bottom of combs. Photo (c) Filipe Salbany 2021

Filipe “handling” bees. (c) Filipe Salbany 2021

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  Log hives

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Log hives around the grounds

Some of the many things we learned

• He is arranging for DNA testing to learn about their lineage, how isolated they really are etc. Early results indicate a high Amm percentage.
• The deeper into the estate you go, the darker the bees get, though a local beekeeper has recently been trying to plant Buckfast hives round the periphery of the estate claiming “wild bees don’t exist”. Filipe is using barrier (bait) hives to intercept swarms from these interlopers before they contaminate the gene line.
• There is a high level of adaptation to the environment. The wild colonies are small and produce small swarms (~5,000 bees) much more often than the foresters realised – until you start looking, you miss most swarms high up in the canopy. The foresters are now very keen bee watchers!
• Several swarms had multiple queens – one swarm had 9 queens. This reminds him of African swarms. African bees have a further layer of super-superorganism where bees migrate perhaps 200km in merged superswarms, with up to 60 queens. He wonders if European bees could do this as a latent behaviour (but just don’t need to). We asked what happens if there are excess queens. He told us that in Africa, where swarms are large, the bees themselves would choose 1 – 3 queens and the swarm might split into several sub swarms. It’s unknown yet what these British bees do with multiple queens.
• They are storing very little honey over winter, which he doesn’t understand yet, but it doesn’t seem to impact their survival rate.
• People often comment how quickly escaped managed bees regress to the local wild bees (2-3 years of natural selection weeds out the foreign genes). He is seeing an interesting selection factor: in tree cavities colonised by swarms from conventional hives (yellower bees), the bees build comb differently to the real wild bees. They have been selected, by humans, to build flat sheets – which is not optimal for defence or climate control, and they die off quickly in tree cavities.
  • A rewilding project in Germany is seeing 75-80% deadouts over winter whereas Blenheim sees about 18%. The difference seems likely due to the bees the Germans are starting with: they have very few wild bees. Incidentally, the BBKA survey results for managed colonies across Britain this last winter were 18.6% losses.
• Bees tend to look for familiar hive cavities. Wild bees from trees look for trees. Managed bees tend to recognise hives as homes.
• The most popular tree type for nests is oak, by far. There are nests in beech, cedar and probably others I didn’t see but the vast majority are in oak trees. In one place there are 5 nests within 70m.
• An interesting correlation – old trees are more protected, legally, thus better homes!
• One colony survived a lightning strike on the tree, possibly due to its propolis envelope acting as a Faraday Cage.
• One big commercial hive can suck up 40 – 75kg of pollen a year. That’s a huge impact on other species.
• Nests are not usually in rotten wood.
• You can gauge how pure Amm a drone is by looking at its underside. The top is usually black – but hybridisation will show up as stripes underneath.

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Our heartfelt thanks to the Blenheim Estate for allowing us access, and particularly to Filipe – who spent at least 8 hours guiding the two groups of us around, and educating us.

Update: in October 2021 some OxNatBees members were privileged to assist Filipe looking for nests. In November 2021 the Guardian published a story on the Blenheim Bees: they are becoming widely known. This created some controversy as the existence of isolated wild bee populations is an emotive subject, so Guy Thompson has written further details on how this is possible, with particular reference to the Blenheim bees, here.