Observations and Development
Understanding the microclimate of nest boxes to design them better
Observe. Measure. Compare. Improve.
These field observations do not constitute a scientific study and are not intended to establish the general performance of any product. They stem from the concern of bird enthusiasts who wish to better understand, under the conditions observed, the temperature inside different nest boxes during heat episodes. This approach is part of a broader concern about the possible effects of climate change on wildlife.
HIRONBEC publishes all of the data series collected in order to share the observations as they were recorded. The results are specific to the locations, configurations, dates and weather conditions of these trials. They must not be interpreted as a guarantee, a certification or a promise of performance that can be reproduced under other conditions.
View or download the full report (PDF, in French) 4-page PDF in French — opens in a new window
Phase 1 – First exploratory campaign
Period: July 20 to August 20, 2026 (32 days). Parameters: temperature and relative humidity. Frequency: one reading every 60 minutes. Conditions compared: outdoors, aluminium compartment and plastic compartment.
This first series was used to document certain temperature differences and to guide the continuation of the observations. The values below describe only the measurements recorded on the dates and at the times indicated.
| Date and time | Outdoors | Aluminium | Plastic | Descriptive reading |
|---|---|---|---|---|
| July 25, 15:00 | 29.6 °C | 38.3 °C (+8.7) | 29.6 °C (0.0) | Aluminium peak |
| July 31, 14:00 | 29.5 °C | 39.7 °C (+10.2) | 28.9 °C (−0.6) | Aluminium peak |
| August 5, 18:00 | 26.7 °C | 29.0 °C (+2.3) | 37.0 °C (+10.3) | Plastic peak |
| August 18, 14:00 | 29.3 °C | 37.1 °C (+7.8) | 29.8 °C (+0.5) | Aluminium peak |
Phase 1 reading: the differences observed varied depending on the time and the configuration. At certain times, the aluminium showed the largest difference from the outdoor temperature; at another time, the plastic showed the largest difference. Since the sensors were not located at exactly the same level, the effect of the material and that of the position could not be separated. This limitation led to a longer campaign and an improved protocol.
Phase 2 – About 30 days of measurements
Period: August 26 to September 26, 2026. Nearly 1,500 readings were recorded per probe at intervals of about 30 minutes. The descriptive comparison includes an insulated / ventilated aluminium version, a reference aluminium model, a gourd-type plastic nest box and an outdoor probe.
| Series | Readings | Average | Minimum | Maximum |
|---|---|---|---|---|
| Insulated / ventilated aluminium version | 1,489 | 18.4 °C | 6.0 °C | 33.7 °C |
| Aluminium | 1,488 | 18.7 °C | 5.3 °C | 37.8 °C |
| Plastic nest box (gourd) | 1,488 | 18.3 °C | 6.4 °C | 36.1 °C |
| Outdoors | 1,488 | 17.7 °C | 7.8 °C | 26.8 °C |
An observed difference between two maximums: 4.1 °C
During this campaign, the maximum recorded in the insulated / ventilated aluminium version was 33.7 °C. The maximum recorded in the reference aluminium model was 37.8 °C. The arithmetic difference between these two observed maximums is therefore 4.1 °C.
Important: this difference does not mean that the insulated / ventilated version systematically reduces the temperature by 4.1 °C. The maximums may have been reached at different times and under different conditions. These data describe this specific campaign and do not, on their own, make it possible to attribute the difference to any particular design feature.
Transparency: all four series are presented, including the plastic nest box. The aim is to make the observations collected visible and to allow readers to appreciate the differences without concluding that any material or design is generally superior.
Methodological note: an outdoor reading of 2.1 °C on August 26 at 08:36, corresponding to a known, deliberate test of the probes, was excluded from this summary. The data were not collected under a controlled experimental protocol designed to eliminate all external variables.
What we would like to explore further
- Protecting the roof from solar radiation
- Natural ventilation
- Double walls and insulation
- Orientation and position of the compartments
- Interior humidity
- Differences between outdoor and indoor temperature
- Repeating the trials under different weather conditions
Sharing for a better understanding
HIRONBEC wishes to share these observations in order to encourage other craftspeople, manufacturers and bird enthusiasts to document their own installations. Measurements taken in other regions, with other orientations, materials, periods and configurations could help broaden field knowledge.
Sharing data along with their context and limitations can help bird enthusiasts ask better questions about the thermal conditions inside nest boxes.