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Backfilling the brood nest

In everyday English, to “backfill” means to refill. So if you want to plant a bush, bury a conduit, or repair a water main, you dig a hole, do what you have to do, and then put the dirt back in. Simple enough. The meaning is only slightly different in beekeeping, but different enough to be confusing.

In beekeeping, backfilling refers to filling an empty brood cell with honey or sometimes pollen. In other words, a cell that previously held one or more generations of developing bees, is now used to store food.

This may occur at different times of year. For example, in the fall when the colony has finished drone rearing, the drone cells may be filled with honey. There are several good reasons for this: drones won’t be raised again for many months, the cells are the wrong size for workers and, since they are close to the main nest, they are convenient storage areas. A well-stocked pantry right at your finger tips—er—tarsal claws!

But there is another time when bees start backfilling . . . just before swarm season. But first, let’s back up a few weeks.

In the early spring the brood nest expands in a process that is the opposite of backfilling. As the bees use up the nectar and pollen adjacent to the brood nest, they turn those empty cells into brood-rearing cells. This allows the colony to raise many more bees—enough bees to maintain the hive and prepare for winter, as well as enough bees to swarm.

Then, as swarming time gets close, the bees begin backfilling the outermost brood cells with honey. This shrinks the nest size, which in turn decreases egg laying by the queen. It means that, after the swarm leaves, the brood nest will be small enough that the remaining bees will be able to care for it. Backfilling provides a way of scaling down the entire operation so a greatly reduced workforce can still get the job done. Ingenious!

It is important to understand the concept of backfilling if you want to manage swarms. Checkerboarding—a popular but often misunderstood swarm management technique—is based on this backfilling behavior. Checkerboarding should be started at the peak of brood nest expansion, just when the nest stops getting larger and begins to shrink . . . but more on that later.

Just for the record, “backfill” can also be a noun, the name for the stuff you put in the hole, as in “They already capped the backfill.”

Rusty
HoneyBeeSuite

Backfilling a hole with dirt. Flickr photo by Archaeobobalist.

Comments

Herb
Reply

Rusty…Can’t wait to read your post. Would you write a post on using the checker boarding method?

Rusty
Reply

Herb,

That’s the plan. First some theory, then the how-to.

Emily
Reply

From what I’ve read, the queen’s laying also drops off before swarming because she is being fed less and chased around the hive by the workers to get her into flying-fit condition. So could filling more cells with honey be a result of more cells being egg-free rather than a deliberate attempt to shrink the brood nest before swarming?

It doesn’t really matter why they end up doing it as the outcome is the same, but I would love to know how conscious the bees are of their behaviour and its future effects, whether they are on automatic pilot or have some sense of how they are contributing to the future of the colony. Bit of a rambling comment sorry!

Rusty
Reply

Emily,

We will probably never know since we can’t think bee. But I think the activities are related with the workers doing the backfilling and the chasing more or less simultaneously, although some sources say the backfilling may begin up to two weeks before final swarm preparations begin. Once final prep begins, which includes slimming the queen, it is virtually impossible to stop a swarm without significant interference with the colony. One thing that is certain is that the workers call the shots, not the queen.

Emily
Reply

Thanks Rusty 🙂

Jeff
Reply

Can you discuss the Demaree method in the future as well as a swarm prevention method prior to colony swarming once open cells have been dsicovered.

I have read about it yet still not totally certain.

Rusty
Reply

Hey Jeff, glad to hear from you. Just yesterday I was wondering where you’d gone.

Anyway, sure, I’ll do a piece on the Demaree method as soon as I finish up with checkerboarding.

Melissa
Reply

I have been trying to understand what happened in my hive since the bees filled every available cell with honey. The queen laid like a mad woman and the bees filled all the empty cells with the same vigor! I hived a #3 pkg of Italians and had drawn comb for them from a failed pkg last year. I hived them in April and by early June I was having problems with space for the queen to lay. There was very little comb building – because they didnt have to. I question if I had not used majority drawn comb – if this backfilling issue may have come later down the road – what is the answer to the problem of backfilling?

Rusty
Reply

Melissa,

The backfilling is a sign they want to swarm. Swarming is colony reproduction, and their wanting to swarm just shows you have a healthy, vibrant colony. You can pull out some of those filled frames and give them empty frames, which will slow they down a bit. Or you can try doing a split before they swarm. Also, if you have another box you can try checkerboarding, which may slow them down. Once they backfill though, it is harder to prevent swarming. Check for swarm cells to see if that is what is actually going on.

Neshan
Reply

Hi Rusty,

I’m in the souther hemisphere, in Peru, so everything works backwards here. We are in July which technically should be winter and relatively cold… not a real winter. More of a California winter, really. Just cold and humid, but it must get to about the 50s (F) at its coldest. Also we are going through El Niño, so it seems like summer! Odd weather.

Anyway, I’ve noticed something strange in my hive… Backfilling like crazy where the brood should be (center of the b-box). There is nectar showing up where it shouldn’t. My queen is young and brand new, only installed her about 2-3 months ago. No queen cells, ever. No signs of swarming otherwise.

I found that the bees have moved the brood over to one extreme of the hive. If brood in a 10 frame Langstroth is normally in frames 4-7, now it’s more like 6-9. Strange, no? Or have you seen something like this happen before? We are NOT in a nectar flow, nor are we in a dearth. It’s just a comfortable middle ground. Bees are active, but not highly active.

Also, I recently (6 weeks ago) took the super off for varroa treatment. Could that have something to do with it? Reduced room for nectar storage? But their reserves aren’t completely saturated either, so WHY would they be mosaicing (is that a verb?) brood with nectar? Or did they want to get away from an apistan strip? (I couldn’t get thymol or oxalic acid and was desperate). Otherwise there are zero signs of swarming, and it isn’t even the right season anyway. Thanks for any input.

-Neshan

Rusty
Reply

Neshan,

I don’t know the answer to your question. I’ve never lived in an area where the bees could collect nectar in the winter, so I don’t know where they would put it. But you shouldn’t worry about the colony not being centered in the brood box. That’s a human concept. I’ve had many colonies not centered and I just don’t worry about it.

Neshan
Reply

Okay, glad to know about the off-center brood frames not being a significant thing to worry over. Thanks.

Also, I suppose that after long term observation, perhaps we could make a distinction between backfilling and what I have noticed as more of a mosaic thing going on. Backfilling (filling empty brood cells with nectar in an orderly elliptical pattern, gradually reducing the brood circle) might be more indicative of swarming, while mosaicking at “random” with nectar within the brood area might just be brood reduction for the winter/slow season? That’s my hypothesis at the moment.

Thanks again for your input!

OkieQueenBee
Reply

Let’s discuss backfilling at this time of year. In Kansas and surrounding states the major nectar flow is basically done, certainly not swarm season, and the bees are beginning to backfill the brood nest. Is it for a natural break in the brood cycle to help in the reduction of varroa? Is it because the bees can sense the dearth coming on and are taking advantage of every storage space they have available? Lots of frames that need drawn but they show no interest in making wax this time of year. How to get those slow packages to build up this time of year.

Rusty
Reply

Okie,

It’s not either of those things, really. Soon after the summer solstice, the bees make the brood nest smaller. Everything about the colony slows down in preparation for winter. There is no break in the brood cycle (unless the queen is superseded) but the worker bees “know” the size of the brood nest must be reduced and they do this by backfilling empty cells with nectar.

It is unlikely you will get any more drawn frames or wax production from now until winter. It is easier to picture this if you think of six months of colony expansion (winter solstice to summer solstice) and six months of colony contraction (summer solstice to winter solstice).

Here is a post from last year that goes into more detail: Winter is coming and your bees know it.

Dave
Reply

Hi Rusty,
I’m in northern Maryland and have an active, large hive that seemed to overwinter well. I noticed there wasn’t a lot of space for egg laying and checkerboarded earlier this spring. I now have 7 medium boxes and lots of bees. Two weeks ago, I couldn’t find any brood or eggs, just lots of honey, nectar, and pollen–and bees. Before closing it up, I did notice what I think is a new queen (my previous one was marked — this wasn’t). I’m assuming there was an earlier swarm that I didn’t notice? So I put in a couple more new frames and waited a week. Today, I found one frame near the top with some larvae. But again, not a lot of space for new brood. The new frames I put in seemed to be filled in with nectar. What’s going on? And how can I encourage a healthy brood nest? Any advice would be appreciated?

Rusty
Reply

Dave,

First, from your description it sounds as though you opened (or spread the brood nest). Checkerboarding, by definition, has nothing to do with the brood nest but is performed in the honey supers above the brood nest.

The unmarked queen could be the result of a swarm or a supersedure. Backfilling of the nest, as I explain above, is usually a sign of an impending swarm. Even if they swarmed earlier, they may be preparing to swarm again.

It is not clear to be if you have seven mediums devoted to brood rearing or if some of those are honey supers. If you have seven mediums of brood, then I don’t know what you mean by wanting to encourage a healthy brood nest. Sounds like you already have one.

The colony self-regulates its size, and your bees may have decided the colony is large enough for now. Like I said, they may swarm again, or they may be slowing brood production for other reasons.

One other question: do you have honey supers on? Again, it’s not clear to me. But a colony that big needs a place to put the nectar. If they don’t have space they are going to put it on the new frames you give them.

Checkerboarding
Opening the brood nest

Tina Berg
Reply

My first hive is filling the last couple brood frames with honey, should I pull these and replace them with empty frames for them to fill with larvae.

Rusty
Reply

Tina,

You can try, but they will probably fill them with honey as well. It is that time of year that brood nests are contracting, not expanding.

Tina Berg
Reply

I should give more details, my hive has 6 and 1/4 bottom deep frames of brood 7th frame has 3 comb spots. and the 9th frame is half full of honey. I have a second deep on top due to I was told since I found 8 super cells and 3 swarm cells I should go ahead and add it. Now that top one has 6 frames full of honey. Should I exchange the bottom honey frame with a empty on from the top or are they thinking of swarming? Queen was present. Or do I leave it the way it is and let them decide that their nest is big enough.

Rusty
Reply

Tina,

“I found 8 super cells and 3 three swarm cells.” Your bees are not going to supersede and swarm at the same time, so you either have 11 swarm cells or 11 supersedure cells. You don’t say where you are, so it is hard to guess what is happening. It sounds like they might swarm, but I really can’t tell from the description.

Richard Rurup
Reply

Hi: In the article above, you said in early spring the bees use up nectar adjacent to the brood nest. In the next paragraph you said that as swarming time gets close the bees begin backfilling the outermost brood cells with honey. Is the nectar fresh spring nectar, and where do they get the honey from to backfill?

Rusty
Reply

Richard,

In early spring the bees expand the brood nest. Often the cells are already empty, due to the bees having used the food supply during winter. But if any cells remain full, the bees will move it or use it to make room for a larger nest.

By the time swarm season arrives, nectar collection is going strong. Some of the incoming nectar can be used to backfill. You can often see backfill in the nectar stage (unripe and uncapped) if you look for it.

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