Water Collection in Honeybees: The Influence of Weather and Colony Size

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This study shows that water collection increases with colony size and on warm days. It also serves as a reminder that water is a basic resource for brood and the normal functioning of the colony. For the apiary, the message is straightforward: a reliable watering point is worth planning for, with appropriate caution given the semi-controlled experimental setup.

1. The essentials in brief

• In this semi-controlled set-up, colonies with more adult bees collected more water than small colonies.
• Collection increased sharply beyond two statistical breakpoints: 22.3 °C mean daily temperature or 31.5 °C maximum daily temperature.
• These two values describe the same shift in regime in the study’s data. They constitute neither universal biological thresholds nor automatic instructions for all apiaries.
• Below the breakpoint, colony strength and the amount of open brood were particularly closely linked to collection. Above it, temperature, solar radiation and dryness of the air became more important.
• For practice, the main message is simple: provide a reliable water source from the brood-rearing period onwards and monitor its availability on hot, dry days, especially for strong colonies.

2. What the study shows

Understanding how colony strength, brood and weather conditions were associated with the quantities of water collected.

Fig. 1. Predicted relationships between daily water collection, maximum temperature, solar radiation and minimum relative humidity while the colonies were exposed to high temperatures. The curves are model estimates with 95 % confidence intervals, not direct measurements of a physiological requirement. Source: Le Bivic et al. (2025), CC BY 4.0.

The question. The authors set out to quantify variation in water collection at colony level and to determine the share associated with the size of the adult population, with brood and with the weather.

The set-up. The study was carried out in Avignon in netted tunnels. The bees therefore had no access to other water sources and could not bring in nectar from outside. Twenty-four colonies provided a total of 73 measurement days in spring, summer and autumn; some colonies were used over two seasons. Two colonies of different sizes were compared simultaneously. For each, an accessible watering point measured the water taken and a control watering point served to correct for evaporation. Weighings were carried out hourly. The number of adult bees and the brood areas were estimated using the standardised ColEval method.

The quantities observed. The colonies classed as large collected more water on average than the small ones across all three seasons. The highest daily figure measured was 1.39 L in a large colony in summer.

The shift observed with heat. The segmented models placed the marked increase in collection at 22.3 °C mean daily temperature, corresponding to 31.5 °C maximum daily temperature. Beyond this, collection rose above all when temperature and solar radiation were high and minimum relative humidity was low. The authors interpret this shift as a sign of growing demand for cooling of the nest, but brood temperature and the use made of the water inside the hive were not measured directly.

The role of the colony. In the statistical decomposition used by the authors, the number of adult bees accounted for a little over 40 % of the explained variance, both below and above the breakpoint. Below it, open brood contributed a further 19 % or so; above it, maximum temperature contributed around 23 %. These percentages describe the relative importance of the variables in this study’s models: they do not mean that each one causes, on its own, a fixed fraction of the water requirement.

The water foragers. The observed proportion of water foragers decreased as the population grew, up to about 13 000 adult bees, and then stabilised at around 0.13 %. This result suggests that the share of the workforce mobilised varies with colony strength. It does not, however, demonstrate individual specialisation: counts at the watering point are a snapshot indicator, not a census of every bee that carried water during the day.

3. A critical look

Distinguishing directly measured results from plausible interpretations and from practical rules that require further data.

What the study establishes soundly within its set-up. Hourly measurement, correction for evaporation, the comparison of colonies of different sizes and the simultaneous consideration of several weather variables make it possible to show that water collection varies with the adult population, with brood and with heat. The repetition of the measurements over three seasons strengthens the consistency of this trend.

What the tunnel changes. The set-up effectively isolates the collection of free water, but it greatly simplifies the situation. The colonies received neither outside nectar nor water from other sources and were fed ad libitum with pollen and fondant. In an open apiary, nectar, the distance to the water point, wind, shade, exposure, topography and microclimates alter the water balance and the cost of collection.

What the measurements do not show directly. The experiment quantifies the water taken at the watering point but does not track what becomes of it in the hive. It therefore does not make it possible to separate exactly the water destined for larval food, for consumption by adults, for the dilution of stores or for evaporative cooling. The thermoregulatory explanation above the breakpoint is biologically convincing, but it remains here an interpretation supported by the pattern of the data.

The statistical scope. The 73 measurement days do not correspond to 73 independent colonies: 24 colonies were used, and some took part in two seasons. The mixed models account for this structure, but the exact values remain specific to this site, this year and this set-up. The authors also report a few influential observations and present sensitivity analyses, which argues for favouring the general trend over too precise a reading of each coefficient.

4. What to take from this at the apiary

Turning the study’s trends into proportionate precautions, adapted to the real conditions of the apiary.

• Do not wait for the heatwave. Water also plays a role during brood rearing. When an artificial source is needed, it is better to install it early so that the bees can adopt it before the hot spells.
• Watch strong colonies more closely. They generally collected more water in the study. An apiary containing several populous colonies may therefore draw heavily on a watering point during a hot, dry period.
• Use temperature as an alert, not as a rule. Forecast maxima of around 30–32 °C justify checking that supply is continuous, but requirements may already be substantial earlier, depending on brood and microclimate.
• Ensure stable and safe access. The watering point must limit drowning, remain accessible and be maintained. This study does not, however, compare types of water or watering point designs.
• Think at the scale of the apiary. Altitude, shading, exposure, natural sources, flight distance and nectar flow can substantially alter the quantity of free water collected.
• Do not size the supply on the 1.39 L maximum alone. This is a value observed in a large colony under a tunnel, not a standard daily consumption or a prescribed capacity per colony.

Read the original study

Effects of weather and colony size on water collection in honey bee, Apis mellifera, colonies

See also:

• All About Water
• Water collection and storage
• Which water for our bees?
• Beehive insulation put to the test of collective thermoregulation in honeybees
• Setting up your apiary

Bibliography

Le Bivic, P., Alaux, C., Gay, C., Vidau, C., Le Conte, Y., Belzunces, L. P., & Pioz, M. (2025). Effects of weather and colony size on water collection in honey bee, Apis mellifera, colonies. Animal Behaviour, 227, Article 123271. https://doi.org/10.1016/j.anbehav.2025.123271