Warming in the land of the midnight sun: breeding birds may suffer greater heat stress at high- versus low-Arctic sites

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: O'Connor, Ryan S., Le Pogam, Audrey, Young, Kevin G., Love, Oliver P., Cox, Christopher J., Roy, Gabrielle, Robitaille, Francis, Elliott, Kyle H., Hargreaves, Anna L., Choy, Emily S., Gilchrist, H. Grant, Berteaux, Dominique, Tam, Andrew, Vézina, François
• Other Authors: FRQNT team grant, Polar Knowledge Canada, NSERC Discovery Grant, NSERC Discover Grant, Canada Research Chairs
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2022
• Subjects: Plectrophenax nivalis; Snow Bunting; midnight sun
• Online Access: http://dx.doi.org/10.1098/rspb.2022.0300; https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2022.0300; https://royalsocietypublishing.org/doi/full-xml/10.1098/rspb.2022.0300

Rising global temperatures are expected to increase reproductive costs for wildlife as greater thermoregulatory demands interfere with reproductive activities. However, predicting the temperatures at which reproductive performance is negatively impacted remains a significant hurdle. Using a thermoregulatory polygon approach, we derived a reproductive threshold temperature for an Arctic songbird—the snow bunting ( Plectrophenax nivalis ). We defined this threshold as the temperature at which individuals must reduce activity to suboptimal levels (i.e. less than four-time basal metabolic rate) to sustain nestling provisioning and avoid overheating. We then compared this threshold to operative temperatures recorded at high (82° N) and low (64° N) Arctic sites to estimate how heat constraints translate into site-specific impacts on sustained activity level. We predict buntings would become behaviourally constrained at operative temperatures above 11.7°C, whereupon they must reduce provisioning rates to avoid overheating. Low-Arctic sites had larger fluctuations in solar radiation, consistently producing daily periods when operative temperatures exceeded 11.7°C. However, high-latitude birds faced entire, consecutive days when parents would be unable to sustain required provisioning rates. These data indicate that Arctic warming is probably already disrupting the breeding performance of cold-specialist birds and suggests counterintuitive and severe negative impacts of warming at higher latitude breeding locations.