Past and future impact of climate change on foraging habitat suitability in a high-alpine bird species: Management options to buffer against global warming effects

The majority of predictions about the impacts of climate change on wildlife have relied either on the study of species’ physiological tolerance or on broad-scale distribution models. In comparison, little attention has been paid to species' mechanistic responses to fine-grained, climate-induced modifications of habitat suitability. However, such studies would be pivotal to the understanding of species' ecological requirements, and hence their adaptive potential to environmental change which can act as a basis for designing management strategies. We investigated foraging microhabitat selection in a climate-change endangered, high-elevation bird species, the white-winged snowfinch Montifringilla nivalis, during the breeding season in the European Alps. Our microhabitat selection model considered various topographical and ground cover variables, as well as sward height, comparing environmental characteristics within a 5-m radius at foraging and random locations, the latter serving as controls. Foraging habitat selection of M. nivalis was positively affected by grassland cover but negatively by sward height. The response to snow cover was quadratic, with an optimum around 40%; the birds also avoided anthropized (urban areas, roads) sites. We estimated past (1976) and future (2066) climate-driven changes in foraging microhabitat suitability, assuming a progressively earlier date of snowmelt due to increasing temperatures over this entire time span. We then modelled the potential impact of snow-melt (and related sward height) on habitat suitability under two scenarios: maintaining the current situation (i.e. some seasonal grazing) and implementing targeted management (e.g.grazing) in an attempt to mitigate impacts of earlier snowmelt. Predicted foraging habitat suitability (estimated as the fraction of suitable plots) significantly declined over time, with a 23% reduction in the number of suitable plots between 1976 and 2016, and a further 32% loss by 2066. However, model outputs demonstrated that maintaining sward height below 6 cm on breeding grounds (e.g. by grazing) would significantly decrease the predicted loss of suitable foraging habitat. Our study shows that detailed information about patterns of resource exploitation not only allows the identification of mechanistic, functional responses of species to environmental change, but also enables an evaluation of habitat options that can buffer against the detrimental effects of global warming.