FEATURE | research

Pollinator Potential

How to Assess the Size, Strength of Honey Bee Colonies

Why Assess the Size of Honey Bee Hives?

Honey bees are the most important pollinator for blueberries in the Southeast. While other bees and insects including bumble bees and blueberry bees, and even the occasional wasp or butterfly, contribute to pollination, honey bees typically provide the bulk of pollination on commercial farms. This is not because they are the most effective pollinator, a distinction belonging to blueberry bees and bumble bees, but because they can be rented and deployed in high numbers. However, since they are not the most effective pollinators and are not highly attracted to blueberry flowers, they need to be present in relatively high densities to achieve optimal pollination. 

Having a sufficient number of honey bees to achieve pollination is dependent on having healthy, strong colonies. It is thus important to ensure that rented colonies are of sufficient size; if colonies are small, a higher density of colonies per acre may be needed for good pollination. Additionally, prices paid per colony should reflect the size and quality of hives provided by the beekeeper.  

Research in my lab conducted on over 20 farms in Florida found that a farm’s honey bee stocking density was not predictive of the number of honey bees found visiting blueberry flowers on the farm (Mallinger et al. 2021). This was because honey bee colony size varied significantly across farms. When the stocking density was multiplied by the average estimated size of the honey bee colonies, it was a better predictor of the number of honey bees found pollinating blueberry flowers on that farm (Mallinger et al. 2021). Stocking density alone is thus not a good indicator of how many honey bees there are available to pollinate. These results further support the importance of doing hive assessments at delivery and/or during the pollination period.

How to Assess the Size and Strength of Rented Honey Bee Colonies

  Assessing honey bee colonies doesn’t have to involve going into the hive. There are a few ways to estimate colony size and strength ranging in invasiveness and in the amount of time, expertise, and equipment needed. 

• Method 1: Frame Counts: The most invasive method is a frame count, which is typically done with the beekeeper at delivery or with a commercial grader. Frame counts involve pulling out the individual frames within a colony and assessing them for honey bee adults and brood (honey bee eggs, larvae, or pupae). Brood can be identified by filled cells, including capped and uncapped cells, within the honeycomb (Figure 1). A general guideline is that a strong, large hive has 7 or more frames that are at least 60% covered in brood cells (capped and uncapped combined) and at least 25% covered specifically in uncapped brood cells (University of Maine Cooperative Extension). Frames with brood should also be blanketed with adult bees (University of Maine Cooperative Extension). While this method generally provides an accurate assessment of colony size and forager activity, the downside is that it generally requires a beekeeper or a commercial grader to be involved, is time intensive, and is disruptive to the colony. Other methods are good indicators of colony size while being less disruptive to the colony. 

Figure 1. A honey bee frame roughly 60% covered in brood cells including capped and uncapped cells and blanketed with adult bees. 

• Method 2: Cluster Counts: Cluster counts are less invasive and time-consuming but still generally require the assistance of a beekeeper or a commercial grader. With a cluster count, the colony is inspected from the bottom (Figure 2) or top (Figure 3) without removing individual frames. Inspecting from the bottom is most indicative of colony size, as adult bee presence at the top is more affected by weather and time of day. In both cases, after removing the top lid or lifting the box from the bottom, the presence of adult bees is noted in the interspaces between frames. The number of interframe spaces filled with adult bees is counted, with the spaces at the edges counting as half spaces (Figure 2) and counting and adding partially filled spaces as needed (Figure 3). A strong colony will have 7 or more total interframe spaces filled with bees (e.g. Figure 2 and 3A) while a weak colony may only have a couple of interframe spaces filled with bees (e.g. Figure 3B).  The number of interframes filled with adult bees is highly correlated with the size of the colony (Figure 4). 

Figure 2. A cluster count inspection from the bottom (i.e. lifting the hive box from its base and inspecting from the bottom). In this case, all interframe spaces are filled with adult bees. The interframe spaces on the edges, in blue, count as half spaces while the interframe spaces in white count as full spaces. This colony therefore has 9 interframe spaces filled with bees (8 white + 2 blue*1/2).  Photo credit Stan Chabert, UF/IFAS.

Figure 3.  A cluster count inspection from the top (i.e. after removing the top lid and inspecting from the top). On the left (A), the colony has 6 interframe spaces fully filled with adult bees and 2 interframe spaces partially filled with adult bees. After combining the partially filled spaces, the colony would be considered to have 7 interframe spaces filled with bees (6 + 2/3 + 1/3). On the right (B), the colony has 4 interframe spaces each half-filled with adult bees. When combining the partially filled spaces, the colony is considered to have 2 filled interframe spaces (1/2*4).  Photo credit Stan Chabert, UF/IFAS.

Figure 4. The relationship between the number of interframe spaces filled with adult bees, as determined using cluster counts, and the actual colony size measured as number of adult bees. Graph credit Stan Chabert, UF/IFAS.

• Method 3: One-Minute Observations: Finally, the least invasive method, which does not require the assistance of a beekeeper or commercial grader, is to conduct 1-minute colony activity assessments. These assessments involve watching the hive entrance(s) for 1 minute and counting the number of forager bees entering the colony after returning from a foraging trip. This can be done at a distance from the hive box and using a phone or other video-taking device zoomed in on the hive entrance(s) (Figure 5). Videos can be watched later at a slowed-down speed, which can be helpful if activity is high (Figure 6). Because forager activity is highly dependent on weather and time of day, these assessments should only be done between 10 a.m. – 2 p.m. when honey bee activity is highest and when it is sunny with temperatures at or above ~60 F. It is also important to observe all hive entrances, including entrances on the top as well as along the bottom (Figure 6). If activity is high, it may be helpful to observe one entrance at a time, or even half of the entrance at a time, and tally total forager activity across observations. 

On average, during blueberry bloom and in fair-good weather, our assessments found anywhere from 1 to 120 bees returning to the colony in a 1-minute period, with an average of 46 bees per minute. If your colonies are averaging fewer than 40 bees per minute in good weather, they may be smaller in size than typical colonies at that time of year. While this method is more sensitive to weather and time of day, it can be a good indicator of colony size (Goldstein 2023) and has the advantage of being non-disruptive to the colony and relatively easy to do without any special equipment. In fact, 1-minute forager counts were more strongly associated with colony size than other methods such as thermal signatures using an infrared camera (Goldstein 2023). 

Figure 5. Taking a 1-minute video of forager activity at the hive entrance. Videos can be taken from a distance, even from inside a vehicle, and watched later at slow speed to count foragers. Photo credit Maxime Eeraerts, Washington State University.

Figure 6. Hive entrances for two colonies, a smaller/less active colony (A) and a larger/more active colony (B). When assessing larger/more active colonies, it could be helpful to take a 1-minute video and watch in slow motion, and/or conduct two separate 1-minute observations for each half of the entrance. Photo credit Shiala Morales Naranjo, UF IFAS. 

Final Considerations

It is important to note that colonies will vary in size and thus assessments should be done on at least 10 colonies assessed at each farm. The farmer or commercial grader should select the colonies to assess in a systematic or random way, being sure to avoid intentionally selecting weak or strong appearing colonies. If opening the hive, be sure the beekeeper is involved in the process or has given you or the commercial grader permission to do so. While it may be tempting to assess colonies with just a quick glance, forager activity over a 1-minute period is not necessarily easy to predict by noting bees on the outside of the hive box or by a quick glance at the hive entrance. Standardized 1-minute observations of forager activity can be compared to other colonies and farms using the same protocol. If colonies are below average in size and activity, more colonies per density may be needed for optimal pollination and contracts with beekeepers should be adjusted to reflect average colony size. 

References

Goldstein, L. 2023. Assessing Honey Bee Hive Stocking Density and Colony Strength for Northern Highbush Blueberry Pollination. Michigan State University Dissertations & Theses.  https://www.proquest.com/openview/8cffc68008d9730481d7380727914bf4/1?pq-origsite=gscholar&cbl=18750&diss=y. [accessed 20 Mar 2026].

Mallinger R, Ternest JJ, Naranjo SM. 2021. Blueberry Yields Increase With Bee Visitation Rates, but Bee Visitation Rates are not Consistently Predicted by Colony Stocking Densities. Journal of Economic Entomology. 114(4):1441–1451. https://doi.org/10.1093/jee/toab111.

The University of Maine Cooperative Extension. Fact Sheet No. 629, UMaine Extension No. 2079. Honey Bees and Blueberry Pollination. https://extension.umaine.edu/blueberries/resources/pollinator-insects/629-honey-bees-and-blueberry-pollination/. [accessed 18 Mar 2026].

CREDIT:
RACHEL MALLINGER, University of Florida