Another post mortem…

Back in May, I visited the bees at Knockhatch Adventure Park, and there had been a small cast swarm in the bait box. We’d put this in a National, and kept an eye on them. I had last checked them from the outside at the end of August, and they had been bringing in pollen and there was plenty of activity.

Paul had a call from Ben at Knockhatch to say the lid had blown off the hive during Storm Ciara, and the bees were all dead. He sent some photos through and what struck me was the diminutive size of the colony and complete lack of stores. It was almost a carbon copy of the situation in the previous post, so I was intrigued to see if Varroa had anything to do with this. We are interested in these bees as they are from a colony which has been living in an ancient oak on the site, and we wondered if there are any genetic factors regarding Varroa resistance, or whether it is all about the tree. Having bees from a feral colony in a hive is interesting as it’s such a different environment to a natural cavity, so we can perhaps learn from the bees’ behaviour once they are in a hive.

It was a very small colony:

Probably only about 2 cups of bees. We found a broken queen cell, and the queen herself:

She looks a nice size, and in fact, with the warmth from sitting on my hand, she and the worker started to stir. Bees go in to torpor when they are cold so in fact, many of the bees were technically still alive. However, it’s important to remember that bees can only survive as a colony. 100 bees – even if that includes the queen – is not a bee colony. It’s possible we could have revived and fed them, and put them in a mating nuc and seen if they had made it a few more weeks, but there is an underlying principle here. We know this swarm was a cast, and despite issuing early in the season, they still hadn’t built up enough to get through the winter. They may have requeened, but why? They would only do that if there was something amiss with the queen they had. A cast swarm is effectively the “runt of the litter”: in good years, they will survive, and in poor years they will perish. Seeing the volume of combs taken up by brood, the numbers were substantial by the end of the summer but there weren’t enough stores to keep them going. They should be backfilling the nest with nectar, but if they can’t get out, this doesn’t happen and they run out early in the season.

Overwintering successfully requires a number of factors:

  • enough bees to keep the nest/cluster warm and perform hive duties;
  • enough honey above the nest to provide both food AND insulation;
  • enough pollen to nourish the young grubs;
  • enough warm days to get out for foraging/cleansing flights in both autumn and early spring;
  • enough forage available in autumn and early spring
  • low levels of Varroa and other debilitating health issues

Bees prioritise getting the numbers up over summer so that they can gather nectar in autumn, but if the nectar can’t be collected, the stores dwindle quickly as there are a lot of mouths relative to available food. It is easy to help casts build up by feeding them, in fact one is instructed to do so in order for them to make it, but there is a sustainability factor here. If we support all the tiny swarms we get we are favouring honey bees over other species, and putting pressure on the hives we have already. Many many creatures will have struggled in the wet autumn and miserable early spring we have had here in the south east, and that’s before the onslaught of the named storms we have experienced in the last week or so. Here is the inspection board:

There are quite a few mites, but this board has not been removed for 4 months. There is very little by way of frass, so it looks like the queen has not been laying for a while. Bees can survive for many weeks if they are in a cluster as they are not expending much energy, so it’s difficult to tell when the colony effectively died. It’s hard to see bees which are alive and yet know the colony is doomed, but as shown above, there are so many factors that need to be working well for the bees to thrive, we have to be pragmatic if they just don’t make it.

We have some frames with clean comb and this hive and the two swarm boxes will be baited with lemongrass, ready for more swarms. The most important thing is that the colony in the old oak appears to be completely fine, and the bees were flying well today in the sunshine despite the cold. When you compare the massive, ivy-clad trunk the bees originated from, it’s no surprise that bees struggle in our flimsy boxes. Insulating hives with a wooden cover or WBC lifts has worked well with other colonies so this can be done for the next occupant of this National come the autumn.

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