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What Is Honey Bee Swarming? An Essential Guide

A bee swarm in a tree temporarily resting

As spring arrives, honey bees get busy collecting pollen, building comb, and lots more. During this time, the colony may grow fast resulting in a crowded beehive. To make space, part of the hive may swarm to a new location. In this guide, we’ll look at honey bee swarming in depth.

What is a honey bee swarm?

Honey bee swarming occurs when around half the bees in a colony leave to establish a new colony. It is a natural process that is usually the result of a crowded hive.

Swarming is far from ideal for beekeepers who will lose bee stocks. It is in their best interests to create favorable conditions for the colony so that they don’t feel the need to leave. An understanding of why bees swarm will help get ahead of any potential hive issues.

Check out the bee swarming video below:

What causes bees to swarm?

While there is a range of reasons for swarming, the most common one is congestion within the hive. An overcrowded hive can reduce the availability of queen pheromone, stimulating worker bees to build queen cups and cells in anticipation of leaving.

Other triggers for swarming include:

  • A sub-standard queen: As the queen bee ages, her ability to lay fertile eggs reduces. Once worker bees detect a problem, they’ll get to work raising a new queen and eventually leave the hive.
  • Rise in temperature: The arrival of spring usually brings warmer weather. This is usually a trigger for bees to seek out new space.
  • Unfavorable food sources: In some areas, a colony may have access to lots of pollen but limited nectar. This results in idle worker bees overcrowding brood boxes instead of making honey. Be sure to check out our article on honey bee washboarding which often occurs during nectar dearth.
  • Genetics: Sometimes beekeepers can provide the perfect environment for bees and they’ll still leave. This could be a bee strain that loves to swarm.

When do bees swarm?

Bees often swarm in spring and early summer on a warm, fine day. They will usually set off any time between mid-morning and late afternoon. If they don’t find a new home by nightfall, they’ll cluster at a temporary resting point like a tree branch until morning.

Occasionally, bees swarm in the fall if there is a desperate need. This doesn’t leave them much time to establish a new hive with honey stocks to last through winter. Most last swarms tend to fail. 

A cluster of bees on a tree branch during swarming
Swarming bees temporarily wait for scouts to confirm their new home.

Swarming vs. absconding – what’s the difference?

Swarming events result in about half the bees leaving for a new hive while the other half stay where they are. Absconding occurs when the whole colony leaves its hive, often because of an intrusive beekeeper, pests, disease, and other threats.

Swarming is mostly considered a positive activity for bees, a sign that they are thriving. Absconding is always a bad sign for bees and may result in the demise of the whole colony.

An infographic explaining the definition of bee swarming with a picture of a swarm on a branch included

The stages of swarming

  1. Once a hive decides to swarm, they begin initial preparations by building queen cups and queen cells. They are often found on the frame bottoms and contain a fertilized egg from the current queen bee. You can learn more about how a bee becomes a queen here.
  2. During the queen-rearing process, scout bees leave the hive and begin searching for a suitable new home. It needs to have sources of water, pollen, and nectar nearby; a safe location, away from pests, predators, and the elements is also essential.
  3. In the week building up to departure, the queen will have been selected and she will be eating less. This will enable her to slim down and fly easier.
  4. When a fine day arrives, the bees will set off in a swarm. Along the way, they often find a temporary location to rest, such as a bush, tree, or building. Finally, when the scouts give the signal, they head off together and begin building their new beehive. 

Common signs that a colony is looking to swarm

If the hive has a large population and all the frames are fully drawn, then there’s a good chance you’re about to lose bees.

Other cues may include a high drone population, forager bees using the entire width of the entrance, queen cells, festooning bees, and large amounts of honey stored above and in the brood.  

How can beekeepers prevent swarming?

While many beekeepers love swarms that come from another hive, none of them want their own bees to leave. It takes time to rebuild the colony and the season’s honey production will take a serious hit.

Swarm prevention is almost impossible and practically every beekeeper will lose bees at some stage. However, there are ways to reduce the chance of swarming. Identifying warning signs as early as possible and making quick changes are your best options.

An open hand that is holding comb with queen cells.
Queen cells are a sign that a colony is going to swarm.

Hive splitting is the most common tactic, which involves transferring some of the existing frames to a new hive.

Before splitting a hive, you may first want to build up an existing hive. This can easily be done by adding a super which creates space for the colony to keep building. Don’t add these supers too quickly or it can have the opposite effect to what you hoped for.

Before adding more supers, you can also create room for agitated bees by harvesting some honey. This is a good idea if your colony is increasingly storing honey in brood frames.

For disease and pest-free apiaries with more than one hive, the beekeeper can remove some bees from a thriving hive and use it to bolster weaker ones. It is important to use younger nurse bees for this tactic as they’ll be accepted into the new hive. Forager bees know where their original hive is located and will head back.  

Keep in mind that no tactic will work every time. Bees can be unpredictable and their urge to swarm may be too great to control. If that happens, move on and help the remaining bees rebuild.

The 3 types of bee swarms

1. Prime bee swarm

The primary swarm is the most common as it is the first swarm of the season for a hive. A colony often reaches around 50,000 bees when this event occurs, meaning the swarm will be roughly 25,000.

2. Secondary swarm

A secondary swarm occurs when a secondary virgin queen decides to swarm as well. If the original colony contained 50,000 bees, then a secondary swarm may have a population as low as 12,500.

3. Absconding swarm

An absconding swarm occurs when a colony leaves its hive due to problems like disease, pests, and starvation. This phenomenon is sometimes referred to as Colony Collapse Disorder.

Abandoned honeycomb
Pests and diseases are common reasons for absconding.

Commonly asked questions

Are swarms dangerous?

Although honey bees can seem terrifying in a swarm, they are actually in a docile state and you’re unlikely to get stung. With no honey, young ones, or home to protect, they aren’t in an aggressive state. Keep in mind that bees are wild insects and if threatened, they may choose to defend themselves.  

Can bees swarm without a queen?

A colony won’t swarm without a queen as she is needed to lay fertilized eggs which develop into worker bees. Nurse bees will always raise a queen in the existing hive before leaving.

What do I do if a swarm attacks me?

Swarms are highly unlikely to attack unless they are threatened or provoked. If a swarm attacks you, the best option is to run to a nearby building or vehicle and get inside. Although a few bees will get inside, it’s preferable to dealing with thousands outside.

If I spot a swarm, what should I do?

If you aren’t a beekeeper, then it’s best to leave a bee swarm alone. It will usually move on within a day or two, but often quicker. You may prefer to call your local beekeepers association or an experienced beekeeper to remove the swarm.

Never try to move on the swarm as you could get severely stung. Although it may be tempting to kill them or call pest control, keep in mind bee numbers are reducing drastically around the world. We recommend not being part of the problem.

A beekeeper in protective clothing removing a bee swarm
Call an experienced beekeeper if you need bees removed.

Am I allowed to kill a honey bee swarm?

Although it isn’t illegal to destroy an unwanted swarm, we strongly recommend against it. You’ll put yourself in a dangerous situation and end the lives of harmless bees that are a huge benefit to our ecosystem.  

What should I do if the bees move into a building?

If you observe the swarm entering a chimney or wall space inside a building, then the swarm has ended. They are beginning to build out a new hive. It is important to act quickly and call a beekeeper to remove the bees before the colony gets too established. If you know how to deal with bees, consider investing in a bee vacuum if you can’t reach them easily.

Can beehives swarm more than once?

Bees may decide to swarm a second time in a matter of days depending on factors like season, sources of food, and queen availability. Known as an after swarm, a colony may divide in half three or more times in a short space of time. Doing this reduces the hive’s chance of survival due to reduced numbers.  

What types of bees swarm?

The most common type of bee that swarms is the honey bee. It will generally include one queen bee, tens of drones, and thousands of worker bees. The size of the swarm in one clump could be as small as an apple or as large as a big watermelon.  

What can I use to repel a bee swarm without harming them?

If you’re concerned that a swarm is going to settle around your home, it is possible to discourage them without using harmful chemicals. Instead, spray an equal mix of almond essence and water in areas that are likely to appeal to scout bees. This should be enough to encourage them to move on to another location.

How do I trap a swarm?

Beekeepers will often try to attract a swarm into one of their hives using a swarm lure. You can learn how to lure a swarm here.

A bee swarm bait trap full of bees.
Beekeepers love to lure swarming bees.

Summing up

A bee swarm is a natural event in the lifecycle of a honey bee and usually signifies a thriving colony. Beekeepers should stay vigilant and stick to regular beehive inspections in the warm seasons to ensure the colony has sufficient space and to keep on top of any problems.

If you’ve got a swarm temporarily resting nearby and you aren’t a beekeeper, in most cases it’s best to leave it alone. They’ll soon move on to their new home. Of course, if there is a good chance people may get stung, contact a local beekeeper and ask if they can remove them. Beekeepers are usually more than happy to add a new colony to their apiary.  

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