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

Abstract Tropical species worldwide are exposed to and respond to the synergistic impacts of multiple global change drivers, such as climate change and habitat degradation. Yet the underlying mechanisms shaping species' demographic and phenotypic responses to anthropogenic change remain poorly understood. We used an 11‐year mark–recapture dataset from primary and selectively logged forest in the Eastern Himalaya to test how species‐specific microclimatic niches (defined here as the temperature‐humidity space used by each species) predict body mass and survival trends in understorey insectivorous birds. Logged forest was hotter and drier than primary forest, and the arthropod prey community showed compositional shifts in selectively logged forest. In understorey insectivorous birds, the degree of dissimilarity between species‐specific primary and logged forest microclimatic niches was strongly and negatively correlated with survival trends in logged forest and less strongly with body mass trends in logged forest. Our results are consistent with the expectation that microclimatic niche shifts in response to anthropogenic habitat modification impact both demographic rates and body condition, crucial for population persistence under anthropogenic change. Synthesis and applications : By identifying the potential mechanisms underlying species responses to selective logging in a thermally sensitive montane bird community, our study informs how the provision or restoration of specific microhabitats can result in positive outcomes for vulnerable species.