As part of an effort to curb declines in bird populations, most birds in California are protected under the Migratory Bird Treaty Act and California Fish and Game Code. Attempts to minimize impacts of Caltrans infrastructure projects, especially bridge construction, on birds have been costly and resulted in project delays. To predict and avoid such conflict, a framework for understanding population-specific migration and nesting patterns would be helpful but efforts to create such frameworks have been limited by the lack of methods for identifying populations at spatial scales relevant for managers. Using Anna’s hummingbird (a species whose ecology has led to conflicts with construction in California) as a case study, the researchers propose to develop a genetic toolkit to assess population-level impacts of Caltrans projects. Products include: 1) A spatial map delineating populations, allowing planners to understand which habitats vulnerable populations are utilizing; and 2) a low-cost genetic assay for population assignment, allowing for specific assessment from individuals at proposed construction sites. This project provides specific tools to avoid impacts with hummingbirds nesting on or around bridges and serve as a general framework for assessing population-specific impacts of Caltrans projects on bird populations.