Effectiveness of novel artificial seabird nest modules for reducing ambient temperature transfer in a warming climate

Artificial habitat for cavity nesting birds can provide excellent opportunities for research and conservation efforts but may expose species to the negative impacts of warming ambient temperatures with climate change. Artificial nest boxes have been successfully used to monitor the breeding activity of the Cassin's auklet (Ptychoramphus aleuticus), a small burrow-nesting seabird, on Southeast Farallon Island (SEFI) since 1971. Mean monthly ambient air temperatures on SEFI during the summer months have increased at an annual rate of roughly 0.03°C from 1971 to 2022, along with an increase in the number of extreme heat days and average maximum temperature, confirming a warming trend at this seabird colony. Given a projected increase in global temperature, we assessed the effectiveness of traditional wooden nest boxes vs. newer ceramic modules at buffering external ambient air temperatures in normal and extreme heat days across a gradient of microclimates on SEFI. Results from fitting linear mixed effects models indicated that, on average, internal temperatures of wooden and ceramic nests (of comparable size and shape) exhibited similar rates of deviation from ambient air temperature of approximately 0.15°C, even during extreme heat events. Ceramic modules did keep nest chambers cooler by approximately 1.2°C than wooden boxes during extreme events at the warmer, drier southern location of the island. Our results can help guide future efforts to design artificial nests that can effectively provide habitat for seabirds as ambient temperatures increase.