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On an overcast morning in mid-April, biologist Maddy Schwarz parked her truck on a levee near Bedwell Bayfront Park, popped a leopard print eye patch over her left eye and peered through a spotting scope with her right. She then scanned a barren area on a dried salt pond about a hundred feet ahead in search of a brown-and-white bird about the size of a soda can: the threatened western snowy plover.
That dried salt pond, also called R3, is part of the largest active wetland rehabilitation effort on the West Coast. The 50-year project is reverting thousands of acres of land all across the Bay that was once used for salt production to its historic tidal marsh state.
But the majority of Bay Area plovers nest on these dried salt ponds. Experts worry the gradual conversion to wetlands will hamper the recovery of the species.
“It’s a very, very tricky balance,” said Dave Halsing, executive project manager for the South Bay Salt Pond Restoration Project, which started in the early 2000s.
At the same time, endangered species like the ridgway’s rail and the salt marsh harvest mouse rely on the historic tidal wetlands as their habitat. And the tidal marshland will also act as a natural buffer to sea level rise, protecting many of the low-lying communities around the Bay Area from flooding.
Of the total project area, which at around 15,000 acres is slightly larger than the size of Manhattan, anywhere from 50%-90% of ponds will be reverted back to wetlands. Those remaining will be kept dry for the plovers or rehabilitated into deep and shallow ponds for waterfowl.
In addition to habitat loss in the Bay, there’s a lot working against the recovery of plovers, including sea level rise, predators, invasive plants and human disturbance. To combat that local biologists have spent decades surveying the birds and enhancing their habitats.
Now, plover numbers are climbing. An estimated 321 adults were counted during last year’s breeding season in the Bay Area; that’s up by more than 200 birds since 2005. Twenty years ago, there were approximately 1,817 adult plovers across the whole range in the U.S. That number has increased by nearly a third.
But for plovers to be delisted, there need to be a lot more of them. Biologists and salt pond project organizers agree that as the restoration work moves forward, balancing the needs of all bayshore wildlife, including endangered wetland species and plovers, is critical.
“I think just maintaining some sort of biodiversity in this world is really important to keep these animals here for as long as we can,” said Parker Kaye, a snowy plover science biology technician with the Point Reyes National Seashore Association, about working with threatened and endangered wildlife. “They’re the ones that need the most help. So I think putting effort into helping them right now is a really important thing to be doing.”
Why the snowy plover population declined
Though it’s a beloved Bay Area symbol — the local coffee chain Andytown even has a drink named after the little bird — the western snowy plover’s range actually stretches from Baja California in Mexico all the way up to Washington. And they’re shorebirds, so they’re found on the coastline.
In the greater Bay Area, however, there are actually more plovers nesting in the Bay than at the beaches.
“I think they’ve always been in the Bay before humans were there,” said Micah Ashford, the snowy plover range-wide lead at the U.S. Fish and Wildlife Service.
“And then when humans showed up, they just happened to modify the habitat for them in a way that they like,” he added, referring to the industrialization of salt production in the mid-1800s in the Bay Area.
But by the 1970s, there was anecdotal evidence that the coastal population was declining, said Ashford, so researchers started surveying the birds to figure out what was happening.
“It kind of comes back to us as humans, unfortunately,” said Ashford of the bird’s decline on the coast. People planted European beachgrass to stabilize dune ecosystems. The dense tufts overtook beaches, pushing plovers out of their habitat.
Development along the coast, sea level rise and erosion of sand all contributed to the degradation of the habitat opposite the dunes. The beach narrowed, and as their habitat disappeared, so did the plovers.
“And by the time they finished their surveys in the 1980s, there were less than a thousand birds in the state of California on the coast,” Ashford said. The findings led to a petition to list them under the Endangered Species Act, and they were listed as threatened in 1993.
How biologists measure plovers’ success
“So I’m looking at an adult female plover on a former salt pond,” said Schwarz, the snowy plover and least tern program director with the San Francisco Bay Bird Observatory as she surveyed pond R3 in the Ravenswood complex in Menlo Park. “And I’m currently trying to determine if she is sitting on a nest or if she is just sitting to chill.”
The observatory has been conducting weekly surveys at known nesting ponds across the Bay Area during the birds’ March-September breeding season since 2003. Six staff members currently survey over 30 ponds in and around Menlo Park, Mountain View, San Jose, Fremont, Newark and Hayward.
Biologists keep track of nests and regularly check how eggs are doing. They float eggs to determine how far along they are in the incubation process and make note of whether nests have been raided by predators, washed away or, ideally, hatched.
Even if the eggs hatch, it’s a lengthy process to get to that point.
“They don’t make a nest like a traditional bird,” Ashford said, describing how the males scrape little divots on the ground for a female to pick as their nest. “And the male can make up to 50 of them. And she’ll just be like, ‘No, not this one. No, not this one.’ But then they’ll find one they like, they’ll start to decorate it with little bits of shell or different materials, like sticks.”
Then, the female will typically lay three eggs in that nest. She’ll incubate the nest during the day and at night, the male takes over.
If all goes well, thumb-sized chicks hatch 28 days later. The female then heads off to start a new nest, while the male takes care of his little family. If he’s successful, his chicks start to fly about a month later.
Biologists keep a close eye on these baby birds that finally take to flight, also called fledges, because they’re key to tracking the progress of the species.
“So (if) for every male we’re getting one chick…the population will not increase and the population will not decrease,” Ashford said. “If it goes above that, then we’re adding birds to the population. And if it goes below that, then the population is likely going to decline in the next year.”
According to the U.S. Fish and Wildlife Service’s snowy plover recovery plan, for the bird to be delisted as threatened, that rate of one fledge to one male has to be maintained for five years. And this metric doesn’t just apply to the Bay Area: The plan segments the plover’s range on the West Coast into six regions, also called recovery units. That fledge metric must be reached by all of them.
Another key criteria for delisting is reaching 3,000 breeding plover adults across the whole range and maintaining that population size for a decade. That goal is further broken down for each recovery unit. In the Bay Area, there need to be 500 breeding adults. Each May, a census is conducted simultaneously by biologists across the West Coast to get a count of how many adult plovers there are.
Why diverse habitat management is key
Though the number of snowy plovers in the Bay Area has more than doubled since the mid-2000s, predation is one of the biggest threats to their growth. At the Menlo Park pond complex, 37% of nests over the 2024 breeding period were preyed upon by predators, the most common being California gulls, snowy egrets and common ravens.
To mitigate the threat, SFBBO staff report precise predator nest and perch locations that landowners should work to remove.
Another tool for fighting predation is the use of exclosures — cage-like structures placed over plover nests to protect them.
“There are holes large enough for a plover to get through, but not for a predator, say, a raven or raptor or coyote. They wouldn’t be able to reach the eggs from there,” said Kaye, who does the same kind of work that Schwarz does in the Bay, but focused on the coast for the Point Reyes National Seashore Association.
Dealing with predators is just one part of the puzzle in the effort to increase the snowy plover population.
“Evidence indicates that predator management and habitat enhancement are big levers that can really help,” said Halsing, executive project manager for the salt pond restoration project. “And we should try to find ways to do more of that.”
With each restored wetland, plovers lose habitat. In late 2023, a dried salt pond, called R4, in the Ravenswood complex was breached. R4 had supported over 20 nests that spring and summer during the breeding season, and over half had at least one egg hatch. But in 2024, the only monitored nest on R4 was washed away during a high tide.
Plovers are site-faithful and will return to breed in areas they’ve successfully nested in previously. So providing reliably dry areas for plovers to breed on is crucial, said Halsing, particularly to meet the salt pond project’s goal of supporting 250 or more breeding plovers.
“One of the improvements we make is by putting (in) more and better and newer water control structures,” Halsing said. These systems run pipes from the ponds through the levee and out to the Bay. Gates on either side of the pipes can be opened to drain water brought on by high tides or heavy rains.
“Because of the nature of adaptive management, finishing work at a pond doesn’t mean that you’re never going to go back and do more work in that pond again,” Halsing said.
Volunteers and biologists also spread oyster shells on the dry ponds, as the birds use them for camouflage.
But there’s a flip side to creating few highly protected and controlled habitats. Biologists worry that a high density of nests on a few ponds is like putting all the eggs in one basket.
“We’ve been sort of worried that, if that’s the only place that the plovers are being attracted to, if that site ever becomes less desirable for some reason, or if that site ever gets hit really, really hard by predators, then there’s not anywhere else,” Schwarz said about a pond in Hayward that supports the highest number of plover nests in the Bay Area. “We just want there to be as much high-quality habitat that’s enhanced that is spread out throughout the Bay so that they’re not just all staying in one place.”
The matter is made more complex by a patchwork of landowners, including U.S. Fish and Wildlife, California Department of Fish and Wildlife, global food corporation Cargill, NASA, Midpeninsula Regional Open Space District and private landowners. And not all plover management work is done in coordination. In Mountain View, Midpen is in the early stages of studying pond management for the benefit of species like plovers and wetland restoration on their land.
And for the western snowy plover to be federally delisted, getting their numbers up isn’t enough. U.S. Fish and Wildlife Service’s recovery plan states there need to be habitat management plans in place to ensure the bird’s long-term sustainability.
At Eden Landing in Hayward, a study that follows the finite movement of the birds is in its early stages. Using what are called Motus tags, birds are tracked at all hours of the day. Biologists hope that collecting this data over the years will answer questions like how quickly females establish other nests after one has successfully hatched or been depredated, or how many nests they establish in a single season.
“The goal being if we know the answers to these questions, then we can hopefully inform management better,” Schwarz said.
‘It takes a village’
Plover numbers are undeniably increasing. The latest count totaled 2,336 adult birds along the United States’ Pacific coast. In 2005, there were a little over 1,800 plovers.
“It’s sort of just this kind of thought of hope that when we as humans do put our minds to something that we want to see change in and we work on it, that that change can happen,” Ashford said. “I think plovers are sort of like a really good case study of that.”
He points to a population in Del Norte County on the California-Oregon border that is seeing nesting and hatching for the first time since the 1970s thanks to a restoration project in which invasive beachgrass was removed.
A similar project took place at Abbotts Lagoon in Point Reyes in 2011. Tall European beachgrass was removed, and it’s since been replaced with smaller native vegetation like Tidestrom’s lupine and beach morning glory. Now, the area “tends to hold the highest proportion of nests in the (Point Reyes) seashore,” Kaye wrote in an email.
Volunteers can also make a crucial impact. Over the years, hundreds have spread oyster shells on dried ponds around the South Bay. This spring, community members also helped install equipment for the Motus tag study. For people who want to do even more and have working knowledge of radio and electrical equipment, they can consider setting up a Motus antenna on their own property.
“It takes a village,” Ashford said. “It’s not just one site and one set of people…it’s not like I’m pulling strings and making stuff happen. It’s through these really collaborative partnerships that we develop with people – not only public landholders, but private landowners as well.”
The San Francisco Bay Bird Observatory is a nonprofit that offers year-round volunteer opportunities and educational events. For more information, including how to volunteer or donate, visit sfbbo.org.
