This project will monitor the populations of terns and skimmers breeding at selected locations in coastal northwestern Mexico and southern California. It focuses on three species that commonly co-occur and establish significant breeding colonies in the region: Gull-billed Tern (Sterna nilotica), Royal Tern (Sterna maxima), and Black Skimmer (Rynchops niger). Gull-billed tern and Black Skimmer are birds of conservation concern in BCR regions 32 and 33. All three taxa are Species of Special Concern in California. Specifically, this project will (1) collect information on breeding population size (number of breeding pairs) and productivity (number of fledglings per pair) for each focal species; (2) initiate a banding program to uniquely mark juvenile birds of each species and continue ongoing banding efforts at the Salton Sea; and (3) survey selected coastal locations during the non-breeding season to document juvenile and adult dispersal and identify important wintering habitats in northwestern Mexico. Standardized monitoring protocols for breeding colonies and post-breeding surveys will enhance our ability to detect population trends in terns and skimmers in the region and elucidate factors responsible for detected changes, identify important non-breeding habitats and their potential threats, and enhance knowledge of population connectivity throughout the annual cycle. The project also provides field assistance and training for Mexican field technicians and students.