Snow Buntings Maintain Winter-Level Cold Endurance While Migrating to the High Arctic

Arctic breeding songbirds migrate early in the spring and can face winter environments requiring cold endurance throughout their journey. One such species, snow bunting ( Plectrophenax nivalis ), is known for its significant thermogenic capacity. Empirical studies suggest that buntings indeed maintain acclimatization into migratory phenotypes when kept captive on wintering grounds. This capacity could be advantageous not only migrating a environment, but also facing unpredictable weather arrival during preparation breeding. However, migration typically leads to declines sizes of several body components linked metabolic performance. As such, experience some loss as they migrate. Here, we aimed determine whether free-living acclimatized phenotype migration. Using multi-year dataset, compared composition (body mass, fat stores, pectoralis muscle thickness), oxygen carrying (hematocrit) performance (thermogenic – M sum maintenance energy expenditure BMR) birds captured grounds (January–February, Rimouski, QC, 48°N) pre-breeding (April–May) (Alert, NU, 82°). Our results show stores were similar between two stages, while hematocrit thickness lower than individuals. These although tissue degradation may affect flight size, are able (i.e., ) up BMR was higher winter, suggesting costs Arctic.