California Bird Atlas calls for public help to map breeding birds

California leads the nation in bird diversity and the number of wildlife refuges and national parks to watch them in. But the Golden State lags behind 44 other states in mapping where those birds live. This isn't just a matter of pride: bird atlases inform policy decisions around land protection, habitat management and climate resilience. That's why the California Bird Atlas, a collaborative state-wide project that launched in January, is enlisting the public's help to document breeding birds with an inaugural California Bird Atlas Big Weekend running June 4-7.

"Breeding bird atlases are large-scale efforts that tell us not just where birds are, but how birds actually use our landscapes. This initiative is critical to understanding the current status of birds in our state," said UCLA ornithologist Morgan Tingley, chair of the California Bird Atlas Science Advisory Committee.

This first annual California Bird Atlas Big Weekend is an intensive event in which thousands of people will log bird observations and submit them to the world's largest ornithology database. Scientists will study the information submitted to understand how and where birds live in a dynamic world. The event will focus on observing breeding behaviors, such as courtship, carrying nesting materials or caring for young. The atlas is a community science effort to which experts and novices alike can contribute.

"I think the emphasis on behavior is appealing to all levels of birding experience," said Sam Safran, the science director of the California Bird Atlas and a UCLA ecologist who studies how birds in California are responding to changing landscapes. "Devoted birders may take big, intense trips out to the mountains or deserts to track down species that haven't been recorded yet. And more casual birders who already enjoy observing these behaviors as their entry point into birding can log observations during walks in a local park or around bird feeders in their yard."

A breeding bird atlas is a multi-year effort to document the breeding distribution and timing of every bird species in a defined region, providing a time-bound snapshot of where and how birds use the landscape. Breeding evidence is mapped over a gridded landscape using standardized codes, such as "nest with young." These types of atlases were invented in Europe in the 1970s and are typically produced through a combination of volunteer community scientists and paid field technicians. Over the years, breeding bird atlases have found new use powering science on species responses to global change.

"Breeding birds are among the best bioindicators of the health of an overall ecosystem, because they respond quickly to environmental change and are relatively easy to observe compared to smaller organisms like insects," said California Bird Atlas director Van Pierszalowski. "Breeding bird atlases establish a baseline for the breeding status and behavior timing of all bird species across the state over a five-year period."

The large size of California, with its diverse bird species and habitats, makes it a haven for birds and the people who love to watch them. Yet California's size and diversity are also challenges that have previously prevented the creation of a statewide atlas. Only 15 of California's 58 counties have conducted a prior breeding bird atlas, capturing just 17% of the state's land area. All but one of these counties are coastal or adjacent to the San Francisco Bay Estuary, showing an extreme bias toward large population centers.

Historically, atlases required mailing paper records, but contributors to the new California Breeding Bird Atlas have it much easier - they can log observations on their phones using the eBird app, which is already popular with birders. All they have to do is "join" the project via the homepage, then when they open their eBird app, they can choose the California Bird Atlas project and begin entering behavioral observations such as singing, nesting and fledging.

If you can't fit the atlas' weekend event into your plans, don't fret! While the organizers chose June 4-7 because it is peak nesting season around the state, the project has been underway since January and will continue through 2030. Since different birds breed at different times throughout the year, such as great horned owls, who begin courtship as early as November, you can log observations any time.

Such a big project wouldn't be possible without the participation of stakeholders across the state. California Bird Atlas' founding partners include dozens of local Audubon and Bird Alliance chapters and Audubon California, as well as organizations including the San Diego Natural History Museum, Western Field Ornithologists, and the Institute for Bird Populations.