Personality differences in the selection of dynamic refugia have demographic consequences for a winter-adapted bird

For overwintering species, individuals' ability to find refugia from inclement weather and predators probably confers strong fitness benefits. How animals use their environment can be mediated by their personality (e.g. risk-taking), but does personality mediate how overwintering species select refugia? Snow cover is a dynamic winter characteristic that can influence crypsis or provide below-the-snow refugia. We explored how wintering ruffed grouse ( Bonasa umbellus ) selected snow roosting sites, a behaviour that reduces stress and cold exposure. We linked selection for approximately 700 roosts with survival of 42 grouse, and showed that grouse generally selected deeper snow and warmer areas. Grouse found in shallow snow were less likely to survive winter. However, individuals that selected deep snow improved their survival, suggesting that demographic consequences of selecting winter refugia are mediated by differences in personality . Our study provides a crucial, and seldom addressed, link between personality in resource selection and resulting demographic consequences.

THE DYNAMICS OF HISTORICAL AND RECENT RANGE SHIFTS IN THE RUFFED GROUSE (Bonasa umbellus)

ABSTRACTClimate variability is the most important force affecting distributional range dynamics of common and widespread species with important impacts on biogeographic patterns. This study integrates phylogeography with distributional analyses to understand the demographic history and range dynamics of a widespread bird species, the Ruffed Grouse (Bonasa umbellus), under several climate change scenarios. For this, I used an ecological niche modelling approach, together with Bayesian based phylogeographic analysis and landscape genetics, to develop robust inferences regarding this species’ demographic history and range dynamics. The model’s predictions were mostly congruent with the present distribution of the Ruffed Grouse. However, under the Last Glacial Maximum bioclimatic conditions, the model predicted a substantially narrower distribution than the present. The predictions for the Last Glacial Maximum also showed three allopatric refugia in south-eastern and west-coast North America, and a cryptic refugium in Alaska. The prediction for the Last Interglacial showed two separate distributions to the west and east of the Rocky Mountains. In addition, the predictions for 2050 and 2070 indicated that the Ruffed Grouse will most likely show slight range shifts to the north and will become more widely distributed than in the past or present. At present, effective population connectivity throughout North America was weakly positively correlated with Fst values. That is, the species’ distribution range showed a weak isolation-by-resistance pattern. The extended Bayesian Skyline Plot analysis, which provided good resolution of the effective population size changes over the Ruffed Grouse’s history, was mostly congruent with ecological niche modelling predictions for this species. This study offers the first investigation of the late-Quaternary history of the Ruffed Grouse based on ecological niche modelling and Bayesian based demographic analysis. The species’ present genetic structure is significantly affected by past climate changes, particularly during the last 130 kybp. That is, this study offers valuable evidence of the ‘expansion–contraction’ model of North America’s Pleistocene biogeography.