<img src=”https://scx1.b-cdn.net/csz/news/800a/2022/analyzing-bird-populat.jpg” alt=”Analyzing bird population declines due to renewable power sources in California” title=”Map of renewable energy facilities in California, USA at which research was conducted. Inset shows the two major western migration flyways of North America (Pacific Flyway in gray; central Flyway in green) that were used with geolocation from stable hydrogen isotope data to define catchment areas (areas holding the sub populations of origin for birds found dead at renewable facilities) to interpret population-level effects. Black solid lines are borders of states and provinces, and dashed lines are borders of Bird Conservation Regions (Coastal California (BCR 32) in blue; Sonoran and Mojave Deserts (BCR 33) in yellow). The Altamont Pass Wind Resource Area (WRA) is composed of approximately 5–30 individual wind facilities located in rolling hills primarily covered with grasslands. See electronic supplementary materials, Methods, for details on both types of facilities…