The boreal forest biome provides a resource-rich environment for breeding birds, supporting high species diversity and bird numbers. These birds are likely to shift their distributions northward in response to rapid climate change over the next century. We used a comprehensive dataset of avian point-count surveys from across boreal Canada and Alaska, combined with interpolated climate data, to develop bioclimatic niche models of current avian distribution and density for 80 boreal-breeding songbird species. We then used a downscaling of projected future climates to assess the potential for these species to change their distribution and abundance in response to climate change. Note that projections represent potential densities based on climatic conditions, land use and topography. They do not account for physiographic barriers such as the northern extent of the Rocky Mountains that may prevent colonization of otherwise suitable habitat. Therefore current species’ distributions may be over-estimated in certain regions, particularly in Alaska.
Boosted regression tree models of species distribution were averaged across two sets of covariates (climate-only and climate + land use + topography), 11 bootstrap samples, and four global climate models. Mean projections and uncertainty estimates (coefficient of variation) are available for the current period (based on climate data from 1961-1990) and three future time periods (2011–2040, 2041–2070, 2071–2100).