Why do Honey Bees Swarm?

Spring time is here and swarm season has begun! It is an inevitable part of beekeeping. Given the impact on a hives’ production, it can be a huge problem for beekeepers. However, it is a problem that can be turned into somewhat of a positive if managed correctly.

For honey bees, swarming is a form of hive reproduction. It happens primarily as a result of hives becoming overpopulated. Lack of space triggers the hive to create a new queen who will leave with 30% to 70% of the hive’s population to seek a new home.

As we begin our conversation about swarming, it is important to clarify the difference between swarming and absconding. Swarming is a natural function of a healthy bee hive. Absconding occurs when the entire colony leaves for any number of reasons. It is generally an indication of a problem in the hive due to various conditions that have made the bees unhappy.

Causes of Swarming

  1. Overcrowding
  2. Poor Ventilation
  3. A failing queen

Overcrowding

As the season rolls from winter to spring, successful queens will increase the number of eggs laid each day resulting in a population explosion in the hive. The number of new bees hatching will begin to grow exponentially. This results in a sense of overcrowding in the hive. This sense of overcrowding can be magnified by the fact that the bees have moved up the hive during the winter.

Many times the lower hive body may be almost completely empty resulting in the majority of the population living in the upper hive body. Since bees like to continually move up instead of down, their sense of overcrowding may be artificial (but try telling that to the bees).

This feeling of a lack of space can also be caused by something as simple as a ring of honey or pollen above the brood area of the comb. This can act as a “road-block” to the queen as she moves around looking for empty cells to lay eggs.

Poor Ventilation

Poor ventilation in the hive can also be a trigger for the hive to swarm. As the hive population grows, heat and humidity can build up inside making the interior less comfortable for your colony. Many hives have an upper entrance that beekeepers will close off during the colder months to help maintain hive temperatures. This needs to be opened back up as warmer days and the spring build-up begins.

Failing Queen

Many hives are triggered to swarm due to a failing queen or a queen that is older. As she moves around the colony, the queen releases pheromones that communicate to her subjects that all is well and this keeps the colony humming along.

If a queen is failing or simply becoming too old, her pheremone production can drop causing mixed signals and a general feeling of uneasiness within the hive. Somehow the workers can detect that there is a problem. This can cause the workers to generate queen cells. These queen cells many times are meant to be a replacement for their current leader but can also lead to swarming.

Pros and Cons of Swarming

Pros

Really there are only two pros to your hive swarming. First, it is generally a sign of a healthy, productive colony. The second is the expansion of your bee yard, and that only happens if you are lucky enough to catch the swarm. Swarms will typically land in the vicinity of the home hive where they will rest in a cluster until the scout bees lead them to their new home.

They may stay in one location for up to 48 hours or they may move from one location to another generally in the same area. During this time, they are normally quit docile and tend not to be very defensive.

Cons

Now for the bad news. While swarming is a general indicator of good things happening in your hive, the result is usually not so friendly. Honey bees that are planning to swarm will gorge themselves with honey prior to their departure. This removes critical stores from the original hive which will invariably be dependent on those supplies.

Also, a swarm will leave with anywhere from 30% to 70% of the current population. While this typically occurs early in the season as the hive population rapidly grows, it will leave a population behind that are very young bees that may still be “house bees” that have not transitioned to foragers yet. This will hurt the hives ability to replace the supplies taken by the bees that left.

Swarms that occur too late in the season can doom the hive to failure due to a shortage of foragers and inadequate time to replace those lost stores. Adding to this problem is the delay in production by the new queen. Typically the old queen leaves with the swarm. The new queen will still need time to take mating flights and ramp up her egg laying which can further endanger the recovery of the original hive.

Adding one last insult to injury is the success or lack there-of with a captured swarm. If you are lucky enough to capture the swarm and re-home it, it still may fail. Also there is a risk that the new home you provide will not be to their liking and they simple abscond for better accommodations.

Remember, the old queen leaves with the swarm. If the hive swarmed due to poor queen performance, it is likely that her poor performance will continue resulting in more problems and likely failure. A lot of work for you to establish a new colony without any reward. Swarming is a tough business.

Prevention

There are no guarantees in swarm prevention. All a beekeeper can do is to make every effort to provide support and proper conditions for your colony to be successful.

To avoid over overcrowding (or the bees sense of overcrowding), there are a few tricks you can use. First, as the spring build-up begins, reverse your hive bodies to redistribute the available space. Bees like to move up and will typically be crowded into the upper hive body coming out of winter. This switch will provide the room needed to continue this upward movement.

Also, add suppers to your hive before they are needed. A good rule of thumb is to add supers when both hive bodies have 7 or 8 frames full of brood and food stores. This will allow the bees to begin storing their food in the super, leaving the frames in the hive bodies strictly for brood production.

Ventilation can be improved by ensuring that the notch on the front of the inner cover is open. This will also benefit you by having a second entry point for foragers returning with nectar and pollen. You can also add small spacers on the four corners of the inner cover which will provide the additional space for adequate air flow.

A few more recommendations include: make sure that you have a nearby water source for your bees. This is used by the bees to help control the temperatures inside the hive as the weather gets warmer. During hive inspections, remove any and all queen cells that are in the hive. Swarm cells are typically found on the bottom of the frames. (Queen cells located on the sides of the frames are supercedure cells and indicate a much bigger problem due to a failing or failed queen). And lastly, hives with young queens are much less likely to swarm. As it relates to swarm prevention, this takes a little planning and it is best to replace the old queen with a young one in the fall of the year. This method allows the hive to build up in the spring with a young productive queen without any downtime.

With all this being said, remember that swarming is a natural process of healthy productive hives. If you have bees, you will have swarms. Managing the process will lead to less disruption in your honey production and may well lead to the expansion of your bee yard. Good luck!

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