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. The California Bird Atlas is an ambitious five- year project to survey and document breeding birds throughout the state of California. The project launched on January 1, 2026, and the fieldwork phase will run from 2026 through 2030. Through the use of eBird, volunteer birders will map the location and abundance of birds breeding and wintering in California. Visit the California Bird Atlas website to learn more about this project. If you are already an eBird user, it is easy to join.
California is divided into approximately 16,500 atlas blocks (about 3 × 3 miles each). Atlas blocks are based on 7.5’ USGS topographic quadrangle maps that are broken up into 6 smaller blocks (two columns by three rows). Each block serves as a survey unit, and is named with the name of the topo quad followed by the position of the block within the quad. See this example of breeding bird data recorded in the block named Goleta NE. In Santa Barbara County, there are 317 blocks. Zoom in on this map to see all blocks in California:
More on Atlas Blocks
If you are a regular eBird user you are already familiar with Hotspots. Atlasers may encounter conflicts when using a Hotspot that is intersected by multiple block boundaries. It is important to keep the observations on each checklist within a single atlas block. If you see that you are about to cross a block boundary (visible in the eBird mobile app), stop your current checklist and start a new one once you are in the new block. This may require you to create personal spots. It might be helpful to plan in advance by comparing Hotspots that you frequently use to block boundaies:
