Broad and Fine Scale Range Shifts of a Species at Risk Across North America

Changes to the distributions of bird populations are becoming increasingly common as climate change and habitat loss continue to alter environments at a global scale. Grassland habitats have been disproportionately impacted by these stressors, leading to unprecedented declines of grassland bird species. Many grassland birds, such as the long-billed curlew (Numenius americanus), have wide ranges across North America, and thus may face different threats and pressures in different parts of their range. Community science databases, such as eBird provide large-scale, long-term temporal and spatial data, allowing for studies that examine changes in species distribution both regionally and range-wide. Using 13 years of eBird data, we examined changes to the long-billed curlew breeding range boundaries and centroid position in North America, and centroid position within eight Bird Conservation Regions (BCR; groupings of similar bird communities and habitats across North America) in which the species occurs. We found an overall northward range expansion of approximately 198 km. At the BCR scale, the Northern Rockies (BCR 10) also showed a northern centroid shift. The Prairie Potholes showed an eastern centroid shift, consistent with a declining population in the northeast Canadian portion of this BCR. Furthermore, we found a pattern of western centroid shifts in several BCRs, consistent with grassland loss in eastern North America. These results reinforce the importance of understanding both range-wide and regional population dynamics to effectively manage at-risk species.