Why do Honey Bees Swarm in Fall?

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One behavior that beekeepers are often surprised to witness is bees swarming in Fall. Finding a swarm can be an exciting time for beekeepers but it is not always a welcomed sight. If you see a bee swarm in August or later, it means they are taking on a risky adventure. Late season swarms have a reduced chance of surviving through Winter.

Small Fall honey bee swarm in tree image.

Swarming in honey bees is a natural process where one strong colony divides into two parts. Ideally, each new half grows into a strong colony. For the beekeeper, this can mean the opportunity to set up a new hive. However, swarming puts both halves at risk as both have to reestablish their home and work force.

Autumn Bee Swarms Face Special Challenges

We beekeepers love to catch wild bee swarms and give them a good home. In most cases, the late season bee swarm is not a bonus for the beekeeper.

We often wonder if the effort to collect it is time well spent. But, most of us do it anyway – because we are beekeepers. That’s what we do.

Odds are against it growing into a healthy colony on its own. In fact, depending on the region – they may not survive Winter.

Dangers of Fall Swarms

There are several reasons that a late season bee swarm may not be a great opportunity for the colonies involved or the beekeeper.

  • fast approaching months of cold weather
  • lessening food resources
  • need to get a new queen mated
  • rearing more workers before cold
Mass of swarming bees flying image.

Can the Bees Get Ready for Winter?

Winter is coming soon. As the days grow shorter and cooler, it will become more difficult for the bees to collect needed hive resources.

They do not have as many foraging hours when the temperatures are warm enough for flight.

Winter food must be stored and in most cases (for a new swarm colony) – the bees must draw comb.

For the actual foundation or structure of the hive thousands of hexagonal honeycomb cells must be built.

While most locations do have Fall flowers that feed bees, the nectar availability may be spotty or non existent.

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In some cases, the older mated queen leaves with a swarm. But, the shorter days signals a time when queens tend to slow egg laying. While the colony need many new workers to help get all the work done.

Even in the perfect situation where the beekeeper feeds the new swarm – there is a lot of work to do. Can the swarm build up enough to survive? In many cases, it will not.

Risk to the Mother Colony

If the Fall swarm came out of one of your own hives, that hive too is now at risk. The mother hive must make a new queen from queen cells left behind.

Their survival depends on her being able to leave the hive and mate with drones – returning to fulfill her role as queen. This needs to be completed in time to rebuild their colony population and replace lost workers.  

Swarming workers leave with full honey stomachs so those food resources must be replaced for the mother hive before Winter arrives.

Beekeeper Intervention

Beekeepers hope for strong Fall colonies with plenty of stored honey. These hives are rearing new fat bees to survive the long cold months.

Their boxes are full of stored honey and pollen. Trying to devise a way to feed these beehives during Winter should not be necessary.

Any hives that are short on food stores should have been fed properly in Fall by their beekeeper. Wild colonies will likely not have a beekeeper to help them. Therefore, their survival numbers are lower.

When a strong Fall colony throws a swarm, this can mess up all your good plans. Still, we have to work with the bees natural behavior.

Catch the swarm if you can and want to but be prepared to offer a lot of assistance to give it a chance of survival.

Factors Contributing to Fall Swarming

Does the influx of fresh nectar from fall plants play a role? Perhaps, a great burst of incoming food might cause some crowding in the hive.

Or an over-productive queen laying thousands of bee eggs late in the year could be the cause.

Colonies that have large infestations of pests often swarm or even more likely – abscond from the hive. Perhaps this is a last ditch effort to abandon ship and try to find a better location.

Pest problems can also be a reason that new bees leave when placed into a hive setup.

The status of the queen may also play a role. If the mother colony is strong – instead of the bees killing the old queen to replace her – sometimes the hive with split and swarm.

This forces a new queen for the original colony and the swarm may requeen itself at the new location.

Why do Colonies Swarm Late in the Season?

Well, do we really know why bees do anything? There are still many questions regarding bees.  Sure we see patterns and understand why bees react to certain stimuli. 

We know that bees communicate with pheromones and adjust the daily workload to the needs of the colony. But, we still have so much to learn about honey bee behavior.

Bee researchers are not certain why colonies throw Fall swarms. But, these Fall swarms are different from the reproductive Spring prime swarms and often much smaller.

Catch Small Fall Swarms for Emergencies

Even if the beekeeper does not intend to overwinter the small swarm, there is still some value in catching it.

If a queen is present, the small colony can be placed in a nuc box for a while. The queen and even the bees with her may be needed in another colony-that is hopelessly queenless and weak.

In this way, you can attempt to save the bees in the swarm, even if they don’t become a separate, stand alone hive.

My September Bee Swarm

It is late September, a couple of years ago. I see a small swarm in a tree. I do not know if it has recently issued from a hive or has been up there for a week or so. It is the size of a small cantaloupe melon at best!

As the beekeeper, I am faced with a decision. This swarm has almost no chance of building into a viable winter colony. If I do nothing, the swarm will most likely die.  

The beekeeper who tries to save these small swarms must be prepared to feed the bees heavily And, it may still be necessary to combine smaller colonies together before cold arrives.

Using my Bucket to Catch the Swarm

The first thing- get the bees out of the tree. Using my “bucket on a pole” I reach up about  12 feet and bump the limb to knock many of the bees into the bucket. These bees are quickly dumped into a box containing 5 frames of drawn comb.

Small Fall bee swarm captured in bucket enters hive image.

This is called a NUC box and is half the size of a regular 10 frame Langstroth hive. It is a good idea to match the size of the box to the bee population. A large box would be too much room for this small swarm to defend.

Do I have the queen? YES I DO. A few minutes later, the queen is inside and some of the bees that I dumped in have come outside to inspect.

Then, they begin to “scent” at the front signaling their sisters to come down. These bee pheromones are wonderful method of communication.

I am seeing more bees at the front door ! They are scenting to call down the rest of the bees still on the limb!

Catching small fall swarm in a nuc box image.

A temporary feeder jar with some sugar water is placed on top. Once most of the swarm is inside, the entrance is reduced to a tiny opening – approx 1 inch in width. 

Hopefully the bees will realize this is the best chance available for them and stay in the box provided. Once dark falls, I move the box to the bee yard. 

Ok, I can say I tried to save them. As I tell students in my online beekeeping class – you can’t save them all!  


How is a Fall swarm different from a Spring swarm?

Both are methods of colony reproduction. However the main reproductive swarms of Spring as generally much larger and do not represent as much of a risk to either part of the hive.

How can beekeepers identify the warnings of Fall swarming?

Routine hive inspections throughout the seasons help beekeepers see any signs of Fall swarms. If the colony begins to build queen cells – look out!

How can beekeepers ensure the health and survival of Fall swarms?

While there are no guarantees, making sure the swarms are well fed, have a mated queen and are housed in an appropriate hive goes a long way towards increases their changes of survival.

Final Thoughts

Honey bee colonies that swarm during Spring buildup are called reproductive swarms. They have a better chance for survival. But, when bees swarm in late August and into Fall, their survival is unlikely.

We don’t know for sure why bee colonies do this risky behavior. Perhaps the colony is reducing the number of bees in their hive or just wanting to make a new queen?

Either way, it is surely a part of the big bee plan that we beekeepers can only puzzle over. Some of their actions remains a mystery – even to those of us who marvel at their amazing life.