Microclimatic niche shifts predict long-term survival and body mass declines in a warmer and more degraded world

Abstract The synergistic impacts of climate change and habitat degradation threaten tropical species worldwide. However, how species’ microclimatic niches affect their demographic and phenotypic responses to anthropogenic change remains poorly understood. Using an 11-year mark-recapture dataset from primary and selectively logged forest in the Eastern Himalaya, we investigated how species-specific microclimatic niches predicted body mass and survival trends in understorey insectivorous birds in each habitat. Overall, logged forest is hotter and drier than primary forest, and the arthropod prey community shows shifts in composition upon selective logging. For understorey insectivorous birds, the degree of dissimilarity between species-specific primary and logged forest microclimatic niches was strongly and negatively correlated with survival and less strongly with body mass trends in logged forest. Microclimatic niche shifts in response to anthropogenic habitat modification can impact both demographic rates and body condition, crucial for population persistence. Our results can inform prompt, targeted conservation efforts toward the most threatened species in a warmer and more degraded world.