The Central Valley Matters for California’s First Statewide Breeding Bird Atlas
California’s Central Valley is one of the most important bird landscapes in North America and one of the hardest to fully “see” with the data tools we rely on most. It is a vast, working mosaic of wetlands, riparian corridors, orchards, row crops, rangelands, canals, and remnant native habitats. It is also a region where conditions are changing fast: water availability is shifting, land use is evolving, and bird populations and breeding behaviors are responding in real time. If California is going to make smarter conservation decisions in the years ahead, we need a clearer, more geographically complete picture of which birds are breeding where, when, and under what conditions. That is exactly what California Bird Atlas (CBA), a new independent nonprofit, is coordinating through the state’s first-ever statewide Breeding Bird Atlas.
A Breeding Bird Atlas is a structured, statewide effort to document breeding birds using behavior-based evidence, not just presence. Participants record observations tied to breeding activity such as courtship, nest building, feeding young, and fledglings, and those records are mapped across a consistent grid. The result is a powerful baseline that land managers, agencies, and conservation groups can use to detect change, identify priority areas, and track how ecosystems are responding to climate pressure and habitat loss.
Most states have completed at least one statewide Breeding Bird Atlas. In fact, 44 of the 50 U.S. states have done so, and many have completed more than one. California, however, has largely relied on a county-by-county approach. Those county atlases have produced invaluable work, but coverage has been uneven and often difficult to sustain. Only 15 of California’s 58 counties have ever completed and published a Breeding Bird Atlas, leaving more than 80 percent of the state without this gold-standard, fine-scale breeding picture. That is now changing. As of January 1, 2026, California officially launched its first statewide Breeding Bird Atlas, using a custom eBird platform designed to support standardized, statewide breeding data collection and long-term data management.
Fieldwork for California’s first statewide Breeding Bird Atlas runs year-round through 2030. The aim is straightforward: create the most complete dataset ever assembled on the distribution, status, and breeding behavior of California’s nesting birds. The project combines broad community science participation with targeted surveys in historically under-surveyed regions, including areas where access or low observer density have limited coverage. Participation is open to anyone. Birders across the state are encouraged to join the project and submit their checklists through the dedicated California Bird Atlas portal at ebird.org/AtlasCalifornia.
To make the data consistent statewide, California is divided into approximately 16,500 atlas blocks, derived by subdividing USGS 7.5-minute topographic quadrangles into six equal units, each roughly three miles by three miles. This grid-based structure provides a consistent statewide framework for organizing effort and comparing results across deserts, mountains, rangelands, urban edges, and agricultural landscapes. Observations retain location information suitable for mapping and spatial analysis, and rigorous quality control is applied throughout so the final products are usable for science and decision-making.
For the Central Valley, the opportunity is especially meaningful. This is a region where small shifts in water, vegetation, and timing can translate into big changes for breeding birds. High-quality breeding data can directly inform practical decisions, including restoration priorities along riparian corridors, wetland management strategies, conservation easements, and land protection targeting. A statewide atlas helps ensure the Central Valley is treated not as a blank spot between “better documented” regions, but as a core piece of California’s breeding ecology.
If you bird the Central Valley, you already have local knowledge that is incredibly valuable to this effort. The Atlas provides a shared structure and a simple pathway to turn that knowledge into information that can guide conservation decisions statewide. To get involved, learn the basics and start submitting your checklists through the Atlas at www.californiabirdatlas.org or ebird.org/AtlasCalifornia.
Van Pierszalowski
Executive Director, California Bird Atlas (CBA); van@californiabirdatlas.org
This announcement first appeared in Vol 28. No.4
