Breeding habitat selection by rosy-finches in the San Juan Mountains, Colorado

Climate change is especially pronounced in alpine habitats where Brown-capped Rosy Finches (Leucosticte australis) breed. However, the potential effects of climate change on rosy-finches are uncertain because basic knowledge of their breeding habitat use is poorly known. I examined Brown-capped Rosy-Finch habitat selection along a nested hierarchy of spatial scales during their breeding season. Rosy-finch breeding area abundance was positively correlated with the availability of snow-free tundra and negatively related to snow cover. Rosy-finches preferentially foraged on tundra over snow throughout the breeding season. Early in the breeding season rosy-finches predominantly foraged on tundra adjacent to receding snowfield edges, but by the late breeding season rosy-finches preferentially foraged on tundra far away from the snowfields. These spatial and temporal preferences coupled with other studies suggest that tundra is the primary source of arthropods consumed by rosy-finches and that these tundra arthropods influence habitat use by breeding rosy-finches. A review of potential climate change impacts facing rosy-finches and their alpine habitat indicate that increasing temperatures will result in a slow contraction of alpine habitat, an upward shift and range contraction for rosy-finches, and a probable advancement in breeding onset.