Why Do Bees Swarm So Late in the Year?

David C. asks:

I took my fall honey supers off and two days later I had two different ones swarm here in late September. The first one left before I could get my stuff to catch it, but I was able to get the second one to a nuc box. With 20 hives at this location, I can’t even find which ones they came from. As late in the season as it is, none have eggs and larvae, but all have some capped brood. I also found the queens in most of the hives but not all. Why would they swarm this late in the year? Both the queenless hives and the swarms won’t survive, as fall is here and almost zero nectar now. This just blows my mind why they would do this.

Rusty Burlew replies:

It’s difficult to diagnose from a distance, but your colonies are probably absconding rather than swarming.

Absconding happens every year, although it seems to happen more frequently in some years than others. It’s one of those bee things we don’t fully understand.

We think that absconding happens when the bees see no other way out of a bad situation. They could just stay put and die, or they can make a last-ditch effort to move elsewhere, hoping things will be better. Unfortunately, most absconding colonies won’t survive the winter unless they get caught and fed by a beekeeper.

Although we don’t know exactly what causes absconding, certain conditions seem to trigger it. For example, absconding is more likely to occur after the following events:

• The colony runs short of food because of a prolonged or severe nectar dearth
• The colony has been extremely hot because of excessive warm weather or severe crowding
• The colony has been heavily invaded by predators such as ants, wasps, wax moths, or small hive beetles
• The colony has experienced excessive disturbance by skunks or beekeepers
• The colony has been exposed to repeated or continuous loud noise or bad odors

So, without any peace, with little stored food, or with strong environmental stress, some colonies just say, “Enough is enough.” They leave the bad situation, hoping to find a better one.

It doesn’t seem to make much sense, but the colony probably senses that it’s on a decline and acts in a desperate manner. Since there is little or no chance of getting a new queen mated, the whole colony moves as a unit, which is different from swarming.

Your best bet at this late date might be to combine the colony you caught with another one. Remove the queen if you can find her and use a standard combining technique such as newspaper.