eBirders Help Identify Critical Shorebird Habitat In California’s Central Valley

By Team eBird 23 Oct 2014

Snow Geese take flight in California's Central Valley, November. Photo by Brian Sullivan.

Linda Pittman and Karen Zumwalt have been avid eBirders for several years. “We do it every day,” says Pittman, who’s coming up on 700 species on her life list. “Every bird we see, it goes up on eBird.” But last year the duo stepped it up a notch, posting a combined 2,000 checklists from their home base in California’s Central Valley near Sacramento. They put in the extra effort when they heard through the Central Valley Bird Club that local eBird sightings were going to be used to identify habitat for a new conservation project. “Suddenly, it’s not just another birding trip. You know you’re contributing to scientific data collection and to actually creating habitat for the birds you see,” says Pittman, who teamed up with Zumwalt to plot day trips to the blank spots in the Central Valley that hadn’t received much eBird coverage. “It makes you bird a little harder. It gives you the urge to cover everything.”

And they weren’t alone—the Central Valley Bird Club and its 500 members made a major birding push last year to put up tens of thousands of bird observations, with a focus on shorebirds in the valley’s 500,000 acres of rice fields. It was all part of a massive crowdsourced birding effort to feed data into a first-of-its-kind conservation project—called BirdReturns—in which The Nature Conservancy paid rice farmers to flood their fields in late winter to provide wetland habitat for migratory shorebirds.

An aerial view of Snow Geese in a flooded rice field, Central Valley, CA. Photo courtesy TNC and Drew Kelly.

An aerial view of Snow Geese in a flooded rice field, Central Valley, CA. Photo courtesy TNC and Drew Kelly.

TNC developed the economic model for cost-efficiently renting habitat from rice farmers, but they didn’t know which farmers to approach to get the most bang for the buck in terms of shorebirds. That’s where eBird came in.

Using data from the checklists of Pittman, Zumwalt, and hundreds of other birders, eBird statisticians and computer scientists built predictive models of where 25 species of shorebirds would be present throughout the Central Valley in February and March. The results were like a weather map for birds, showing where clusters of shorebirds would congregate at 1-week intervals, dialed all the way down to about 2-square-mile grids.

These shorebird forecasts, paired with NASA satellite imagery of surface water availability across the Central Valley, made it possible to see where wet habitat was needed. Without this critical habitat, the shorebirds were likely to fly over dry areas and push farther north, in the process further stressing their already-exhausted bodies during migration.

TNC biologists conducted formal surveys to assess the final results, which were a smashing success. During an 8-week period, the Bird Returns flooded rice fields hosted more than 220,000 birds representing 57 species, including every migratory shorebird species in the Central Valley. Recorded shorebird densities averaged well over 100 birds per acre in March, which was 10 times the number of shorebirds found in other areas outside the project. The tallies for individual species included more than 20,000 Dunlin, which represents about 20 percent of their entire Central Valley wintering population—all resting and feeding in wet habitat identified by eBirders.

“This project couldn’t have been situated in a better area for eBird, because the whole region is full of eBird Hot Spots,” says Steve Kelling, information science director at the Cornell Lab of Ornithology.

Now the eBird team is back at it, creating more shorebird occurrence and abundance models for TNC to use in the Central Valley. The second season of BirdReturns, underway right now for the fall migration, is again showing impressive results—daily counts for many species are higher than there were last spring (Long-billed Curlew, Long-billed Dowitcher, Least Sandpiper, Black-necked Stilt, and Greater and Lesser yellowlegs), and some new species are showing up and using the flooded fields (including Caspian and Forster’s terns and Red-necked Phalarope).

The higher numbers may be partially attributable to conditions on the ground—with California in the grips of an excruciating drought, the BirdReturns flooded fields are like oases in a desert. The vision for eBird, says the Cornell Lab’s Kelling, is to provide more such birder-identified habitat oases throughout the entire Pacific Flyway, then throughout North America, and eventually around the world. “This was the original vision for eBird,” he says, “Directly applying birdwatcher checklists to the conservation of birds.”

Flooded rice field, Central Valley, CA. Photo courtesy TNC and Drew Kelly.

Flooded rice field, Central Valley, CA. Photo courtesy TNC and Drew Kelly.

eBird would like to extend special thanks to NASA, the Leon Levy Foundation, and the Seaver Institute for grants and funding that supported the development of shorebird predictive STEM models for this project. eBird also greatly thanks all the birders of the Central Valley Bird Club for their incredible volunteer effort to feed these models with high-quality data.