Weather and land cover create a predictable “stress-scape” for a winter-adapted bird

Abstract

Context: Variability in temperature and snow cover are characteristics of high-latitude environments that impose significant pressures on overwintering species. To cope with increased energetic demands and decreased resources, species occupying seasonal environments often seek out refugia that buffer them from inclement conditions. Ruffed grouse (Bonasa umbellus) roosting in the thermally stable microhabitat beneath deep snow are buffered from negative effects of cold temperatures on physiological stress (glucocorticoid hormone levels). Objective: Despite physiological advantages of accessing warmer refugia during winter, it is unknown how land cover and winter climate promote the occurrence of such refugia over space and time. Analogous to the landscape of fear, which mediates how prey navigate spatial variation in predation risk, mapping a landscape of stress, or stress-scape, may identify hotspots where metabolic challenges persist. Methods: We assayed droppings for fecal corticosterone metabolites (FCMs) collected from radio-tagged ruffed grouse over three winters and developed a spatial model of FCM concentrations across the extent of our study area, thus quantifying a stress-scape. Results: FCMs increased with shallower snow depths, less dense snow, colder ambient temperatures, and more open habitat. However, despite considerable spatiotemporal variation in snow depth, snow density, and temperature, the regions across the landscape where grouse had elevated FCM levels were consistent and predictable across years. Conclusions: Stress-scapes offer a new tool for understanding and quantifying indirect effects of stressors and can identify areas of the landscape where there may be consistent hotspots of stress that are the result of multiple ecological and environmental challenges.