California is home to more species of breeding birds than any other U.S. state, underscoring the state’s ecological richness and broad range of habitats. To better understand and protect this biodiversity, especially in the face of accelerating environmental change, California Bird Atlas (CBA), a newly formed 501(c)(3) nonprofit, has announced the launch of California’s first comprehensive statewide Breeding Bird Atlas.
Breeding Bird Atlases (BBAs) are systematic, multi-year efforts to document the distribution, timing, and breeding behavior of all bird species within a defined region. As highlighted in California’s 2025 State Wildlife Action Plan, BBAs “support SWAP goals by filling critical knowledge gaps on species distributions, habitat use, population trends, behavioral shifts, and connectivity—all essential for habitat management, conservation planning, and climate adaptation.”
While 44 other U.S. states have conducted at least one statewide BBA, California has historically approached this work at the county level. Though these efforts have produced valuable data, only 15 of the state’s 58 counties – mostly in coastal or urban areas – have published Atlases. As a result, over 80% of California’s land area has never been surveyed using this globally recognized gold-standard approach to systematically documenting breeding birds.
To address this gap, this landmark initiative will begin year-round fieldwork on January 1, 2026, and continue through December 31, 2030. Over those five years, the project aims to produce the most complete dataset ever assembled on the distribution, status, and behavior of all breeding bird species across California’s habitats and counties. It will combine broad-based community science with targeted surveys, particularly in historically under-surveyed regions. Data will be collected primarily through a custom-built eBird Atlas Portal, developed in collaboration with the Cornell Lab of Ornithology.
To structure the survey, California will be divided into approximately 16,500 atlas blocks, created by subdividing USGS 7.5-minute topographic quadrangles into six equal units, each about three miles by three miles. This grid-based framework will ensure consistent spatial coverage across ecosystems including deserts, rangelands, mountains, and coastal habitats. All observations will be georeferenced with precise latitude and longitude coordinates, enabling robust spatial analysis at multiple scales. Rigorous quality control measures will be applied throughout the project to ensure scientific integrity and usability of the data.
CBA’s Science Advisory Committee is chaired by Dr. Morgan Tingley, whose lab at UCLA’s Ecology and Evolutionary Biology, University of California, Los Angeles will lead project methodology and design. The Committee includes representatives from leading voices from state agencies and research institutions across the state. Members include Melanie Gogol-Prokurat (Lead Scientist, California Natural Diversity Database, California Department of Fish and Wildlife) and Ron Melcer (Environmental Program Manager, California State Parks), ensuring the Atlas is well-integrated with California’s broader biodiversity monitoring priorities and conservation planning frameworks.
If you'd like to learn more about the project or get involved, please visit the California Bird Atlas website.