Turn up the air, turn down the heat: designing sustainable birdhouses to reduce heat stress in birds

Rising temperatures associated with climate change pose increasing concern for many wildlife species, including nesting birds. High temperatures can negatively affect nesting success, chick body condition, and chick survival in artificial birdhouses. Threshold high and low daily temperatures or large fluctuations within a 24-hr period can influence bird stress and chick survival.

The purpose of this project was to build, test, and evaluate the effectiveness of a novel birdhouse design that takes advantage of convection currents and thermal buffering to reduce temperatures within artificial nest boxes. By lowering internal temperatures, the design aims to decrease heat stress and potentially improve nesting success.

Hypothesis: the convection current birdhouses would perform better (lower temperatures) than the standard birdhouses, because there would be a thermal buffer and air flow with colder air going in through the bottom and hot air leaving through the top

The materials used for this project were:

•       12 identical-sized wooden birdhouses, 6 convection boxes and 6 standard boxes

•       14 HOBOs (Onset® Temperature Data Loggers)

•       Computer with Microsoft Office (Word, Excel, and PowerPoint)

•       Phone with HOBO® Connect app

•       Rite in the Rain journals

•       Writing implements

•       Biorender®(scientific imaging and illustration software)

Standard and convection birdhouses were paired on a post. Half of the birdhouses were set facing north, while the other half were facing south. Two control HOBO©s were included. The HOBO©s recorded a data point every hour.

We transferred the data from the HOBO® Connect app into an Excel database. We averaged the samples for each birdhouse type and the control and graphed the data to compare the results.

We used linear regression to investigate the influence of time of day, aspect, and birdhouse type on temperatures. Based on these results, we separated data into day and night data sets for further comparisons. We then calculated the maximum, minimum, and diurnal temperature range. We then used a student t-test to test for differences between standard and convection birdhouses for each of these temperature measurements.

Lastly, we compared standard and convection birdhouses by counting the number of days that temperatures reached critical thresholds known to affect bird stress, nesting success, and survival. We used a maximum daily high temperature of >30, a minimum daily low temperature of <5, and a diurnal temperature range of <15 degrees Celsius as biological thresholds.

Using hourly data and linear regression, we found that temperature was significantly influenced by birdhouse orientation, design, and time of day (F₃,₂₈₂₇₈ = 2972.21, p < 0.001), with the model explaining 24% of the variation in temperature (R² = 0.24). Overall, time of day had the strongest influence on temperature. For this reason, we divided our data into night and day to further compare the effects of standard and convection birdhouses on temperature.

Maximum daily temperatures differed significantly between birdhouse designs (t₁₁₇₇ = −5.88, p < 0.001; Figure 2). Convection boxes exhibited lower maximum temperatures (21.17 ± 0.17°C) compared to standard boxes (22.71 ± 0.19°C), representing an average reduction of approximately -1.54°C. Minimum daily temperatures were slightly higher in convection boxes at night (9.87°C) compared to standard boxes (9.41°C), representing a difference of 0.46°C (t₁₁₇₄ = 1.84, p = 0.066; Figure 3). Diurnal temperature range differed significantly between birdhouse designs (t₁₁₇₄ = −5.31, p < 0.001; Figure 4). Convection boxes exhibited a smaller daily temperature range (11.49°C) compared to standard boxes (13.13°C), representing a reduction of approximately 1.64°C.

There was a -56.1 (41-18) percent decrease in the number of days where maximum daily temperatures were greater than 30° in the convection boxes. Minimum daily temperatures had a percentage decrease of -28.9 (83-59) reducing the number of times the convection boxes reached the minimum temperature threshold. Finally, the percentage difference for diurnal temperature range was -31.1 (22.5-15.5) keeping a steadier temperature during temperature fluctuations.

Our results during the day supported our hypothesis, however, our nighttime data showed that the convection birdhouses had higher temperatures than the standard boxes. Together with lower maximum temperatures and slightly higher minimum temperatures, these results indicate that the convection design buffered thermal extremes and reduced daily temperature variability. Because nesting success is often most sensitive to extreme heat and time above critical thresholds, these reductions in thermal extremes likely decrease heat-stress risk during hot periods for nesting birds.

Next time, we are planning to analyze the bird’s behaviour towards the birdhouse and if it has a preference of birdhouse. We would also analyze the differences in behaviour from birds using convection birdhouses compared to birds using standard birdhouses in our community.

Thank you to Shannon Crowley, for mentoring us in statistics, Gary Soles for helping build the boxes, Mrs. Boyes for having us practice in front of our classmates, The John Prince Research Forest for lending us the HOBO sensors, Thank you FSJSS for the use of their shop, Saveena Dhaliwal for helping with the animation, and the biggest thank you to the birds - we hope our project will help birds in the future.

Andreasson, F., Nilsson, J., and Nord, A. 2020. Avian reproduction in a warming world. Frontiers in Ecology and Evolution 8:576331. https//doi.org/10.3389/fevo2020.576331

Briga, M., and Verhulst, S. 2015. Large diurnal temperature range increases bird sensitivity to climate change. Scientific Reports 5:16600.

Foord, V. 2018. Climate Patterns, Trends, and Projections for the Omineca, Skeena, and Northeast Natural Resource Regions, British Columbia. Prov. B.C., Victoria, B.C. Tech. Rep. 097. www.for.gov.bc.ca/hfd/pbus/Docs/Tr/Tr097.htm

Horacek, Christopher G. 2022. Temperature Affects Nest Box Occupancy, Nest Success, and Nestling Size in a Southeastern Population of Eastern Bluebirds (Sialia sialis)". Biology Theses. 26. https://kb.gcsu.edu/biology/26

Mueller, A.J., Miller, K.D. & Bowers, E.K. Nest microclimate during incubation affects posthatching development and parental care in wild birds. Sci Rep 9, 5161 (2019). https://doi.org/10.1038/s41598-019-41690-4

Sun, Alice. (2024, August 22nd) How To Stop Nest Boxes From Turning Lethal In Extreme Heat Audubon. Org. Retrieved from https://www.audubon.org/magazine/how-keep-nest-boxes-turning-lethal-extreme-heat

Taff, C, C., Shipley, & R, J. (2023, November 16). Inconsistent shifts in warming and temperature variability are linked to reduced avian fitness. Nature. https://www.nature.com/articles/s41467-023-43071-y