Data from: The conservation value of high elevation habitats to North American migrant birds

The basic patterns of faunal community composition and habitat associations of high elevation mountainous regions are poorly-known. This is true for the avifauna of western North America where our knowledge of high elevation use is primarily restricted to breeding assemblages. Here we report on systematic avian surveys of high elevation habitats over four years in British Columbia conducted during the post-breeding and fall migration periods (Aug–Oct). We detected a remarkable diversity of birds (95 species in 30 families) using alpine, subalpine, and montane forest, many of which used these habitats seasonally. One quarter of the species are on lists of conservation concern. Density, species richness, and community composition varied considerably between habitats and mountain ranges within the study area, especially between the western slope of the Coast range and other ranges. Most species exhibited strong temporal variation in patterns of abundance that were related to migratory behavior. From an extensive literature-based survey, we found that ~ 35% of North America's breeding bird species use high elevations, and that all primary high elevation habitats are important for full life-cycle conservation of this avifauna. Our findings highlight the importance of high elevation habitats to migrating birds from wide-ranging breeding distributions for at least three months of the year, a period equivalent to the length of the breeding season for most species. These results emphasize the need for effective conservation of fragile alpine and other high elevation habitats that are increasingly threatened by local, regional, and global anthropogenic disturbance.