Natural nest cavities in a high elevation habitat provide a more constant thermal environment than human-made nest cavities

Nest cavities with suitable thermal conditions can provide fitness benefits for birds through reduced thermoregulatory cost. Insulation can however vary between natural and human-made cavities. While several studies have assessed cavity temperatures, research from high elevation habitats, where environmental conditions are particularly variable, is still scarce. We compared temperature profiles of vacant natural and human-made nest cavities of White-winged snowfinches Montifringilla nivalis, a high elevation cavity nestling species. Human-made cavities experienced more extreme temperatures, with potential consequences for offspring viability, bringing into question their suitability as conservation measure, particularly as extreme temperature events become more frequent.