Report delivers ominous data on Marin shorebirds

The bird population that relies on estuarine habitats in Marin and throughout the Bay Area is dwindling and needs help, according to a new report.

Shorebirds, which thrive in expansive tidal flats, are experiencing the most concerning decline in the region, the report says.

“It’s quite an alarming drop — anywhere from about 25% to about 85%,” said Julian Wood, a program leader at Point Blue Conservation Science, one of the report’s authors.

The bird population data are an indication that something is wrong in the ecosystem, a particularly worrisome development as the Trump administration shifts focus away from conservation efforts, Wood said.

“Many of these monitoring efforts rely on federal money. If that goes away, we likely won’t be able to continue that monitoring,” Wood said.

The ramifications could include species slipping under the radar into endangered status. That would leave little time and money for targeted restoration, impeding efforts to revive threatened birds, Wood said.

The report — a project of the San Francisco Bay Joint Venture, a public-private partnership, and Point Blue Conservation Science, a nonprofit research organization — is the first of its kind since 2011. It is presented as an interactive website at sfbaystateofthebirds.org that will be updated with ongoing monitoring results, recommended actions and stories of successful habitat restoration efforts.

Researchers focused on what are called “indicator species” in four types of habitats: tidal marshes, tidal flats, subtidal zones and nontidal waters.

In the North Bay, medium-sized shorebirds, such as black-bellied plovers and dowitchers, had the steepest decline over the past 20 years, at 68%. Large shorebirds, such as American avocets, marbled godwits and willets, are down 61% for the same period.

Small shorebird populations didn’t drop as dramatically. Birds like least sandpipers, western sandpipers and dunlins fell by about 26% in the North Bay.

The reason for the drop is difficult to understand, Wood said.

Shorebirds are migratory birds that stop in the Bay Area during the winter to feed and fuel up for their migration to the north.

“While it could be that the habitat in the bay is not adequate, it’s also likely that there are other stops along their route that are not providing good habitat,” Wood said. “It could also mean that there are issues on their breeding grounds where they’re unable to successfully breed.”

Barbara Salzman, president of the Marin Audubon Society, offered a solution.

“We need more restoration and to pay more attention to shorebirds,” Salzman said. “They need mudflats. That’s where they feed, and they need upland areas that are not vegetated.”

It’s an opinion that aligns with recommended actions presented in the report.

The report recommends projects to remove non-essential barriers such as dams, culverts, levees and other structures that inhibit the natural flow and settling of sediment on mudflats, among other types of projects.

Data for birds in the other three habitat types present mixed results.

Some good news is that tidal marsh-dependent birds are increasing overall. These include song sparrows, common yellowthroats and black rails. It indicates that the large movement over the years to restore this type of habitat, including in Marin, is proving to be successful.

One such project is the Hamilton wetlands restoration, which transformed a former army airfield in Novato into 648 acres of tidal and seasonal wetlands supporting more than 100 species of birds.

“What we want the public to take away is the opportunity to celebrate our successes,” said Kelli McCune, director of partnership coordination at San Francisco Bay Joint Venture. “Not only do birds alert us to where there’s potentially problems and habitat types to focus on … but also, importantly, where things are working. I think that’s clearly demonstrated with the tidal marsh habitat results.”

But not all tidal marsh birds are doing well.

The endangered Ridgway’s rail is experiencing a 6% decline regionwide.

“It’s a concern because much of the restored habitat is for tidal marsh, that’s their main habitat,” Salzman said. “So it’s not quite clear why they’re declining.”

The report says the rail’s population can fluctuate and future surveys will reveal if the downward trend continues. Continuing to restore tidal marsh is one of the best strategies to boost its numbers, it says.

In subtidal habitat, diving ducks are stable overall, but the report notes declines in the North Bay and central Bay Area. Their populations have increased in the South Bay.

Rebecca Schwartz Lesberg, president of the San Francisco Bay Joint Venture board, said it’s concerning that diving ducks are declining in the North Bay.

“These are species that rely on underwater habitats like eelgrass that our county is investing heavily in,” said Schwartz Lesberg, who is executive director of the Marin Conservation League. “And so I will be very excited to see the results of those investments in eelgrass and other subtidal habitat restoration as those projects mature and come online in the future years.”

Moving into the deeper non-tidal wetlands and waters, the total number of dabbling ducks has increased over the past three decades across the region. However, California’s breeding waterfowl populations have significantly declined, including mallards.

Schwartz Lesberg said the report provides a bigger picture and a call to action.

“It’s not just birds and wildlife that need clean water and healthy habitats — it’s the millions of people of the Bay Area who rely on these places to live, work and play,” Schwartz Lesberg said. “So we all benefit as people or wildlife when our water is cleaner, when we have more access to nature and open space.”

McCune said another benefit of wetland restoration is flood protection from the threat of rising seas.

“These are all benefits we gain from these restored habitats and being able to be in relationship to nature,” McCune said. “It does take us working together, and we do need funders at all levels, from local, regional, state to the federal level to support this good work.”