What Makes Bees Swarm?

Overcrowded bees swarm. They will leave the hive and find a tree for a day or so until they find a new location to live. “There’s a bee for that.” As you may know, bees each have a particular role in the hive. The “Scout Bee” has the job to find a new home for bees in overcrowded living situations. If you find a random group of tightly woven bees, they will probably be in the shape of a football hanging from a tree limb. They are usually calm when they are in a swarm. It is not difficult to collect them in an empty hive box, add a queen (if necessary) and start another hive.

The thing that looks like a peanut on this frame of brood is a swarm cell, a clear indication that the bees are planning to leave the hive

The image below represents my first swarm. I was in the bee yard with my teacher Mike. The bees were VERY HIGH up in the tree and Mike was standing at the bottom of the tree banging 2 drum sticks together to lure the bees into an empty hive ready for collection. The funny part, the bees weren’t coming. I left that day and looked over my shoulder to see if Mike was still banging the drumsticks together, and he was.

I guess you had to be there. It was funny.

Swarm found at University of Maryland Wye Research and Education Center

Swarming is Unlikely in the First Year

Bees need room to grow. If they are overpopulated early in the spring, they will look for a new place to spread out. If you are tending your bees, you need to take inventory on capped brood and add empty brood frames. This gives the bees plenty to do and it will help to curb swarming. Adding a second brood box in a perfectly timed manner, also allows the bees to climb up and spread out, offering a better chance of keeping your girls home.

Bees like to fill out frames almost all the way capped before they move up. Adding another brood box or splitting the bees making use of Nucleus “nuc” frames and creating another hive is like a gift for the bees. If you are vigilant and stay in touch with the progress of your bees, you can easily grow your colonies, from just helping them expand at the right moments.

Last season we had an incredible start to the season.

The plant material was in full bloom early and the bees were gathering nectar early. We realized, mostly way too late (because they were a month ahead of the years before) that the brood chamber was completely filled with honey! Needless to say, there was a reduction in the workforce because the queen had no place to grow her family. Had we caught this situation in time, and “checker-boarded” the brood chamber with empty frames, the bees could have kept busy and the queen could have kept laying.

Photo by Lloyd Seested of a swarm he found. I’ve never seen one this large before

Bees may also swarm for other reasons that may have to do with disease

Bees may leave to find a new source of food because they are hungry. A mouse may have found its way into the hive causing the bees to flee. Sometimes I notice when there are sharp changes in the weather they leave, or they may swarm due to queen failure. I have heard stories where a beekeeper added a new super to a hive made from “new fresh wood” and the bees swarmed.

When you are a new-bee, it’s sometimes hard to determine the exact reason why your bees are gone. When a hive weakens and the bees die-off, it can appear to have swarmed, when in fact, everyone just died. In my experience (I am updating this piece 9 years after I originally wrote it) when weak hives get robbed by a neighboring, hungry hive, the result can appear to have been a swarm.

What Signs Do You Look for to Prevent a Swarm?

For “new-bees” like me, it’s easy to confuse “bearding” with “swarming”. “Bearding”, is when many of the bees from inside the hive, hang out on the OUTSIDE of the hive. The most prolific beards appear on the hottest and most humid days of summer. The bees are basically sitting out on the front porch to keep themselves and the hive cool. The larger the population, the more you will see bearding in the hot weather. Soon, we’ll learn more about bearding.

Hive Front with Bees Bearding
small beard forming on the outside of a young hive

Collecting a Wild Honeybee Swarm

Next post in this series: Visiting the hives on day 32

About the Author


Kara waxes about the bees, creates and tests recipes with her friend Joyce, and does her best to share what she’s learned and continues to learn about the bees, honey, ingredients we use and more.

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