SAN FRANCISCO, CA) – Rising sea levels due to a warming climate could reduce the already-narrow nesting and foraging habitat of the Black Oystercatcher and threaten its future survival, according to the findings of a study published in Marine Ornithology today, by Audubon California, National Audubon Society, Bird Alliance of Oregon, and Oikonos Ecosystem Knowledge. The milestone study, based on 10 years of data collected in Oregon and California between 2012 and 2022, establishes a first-of-its-kind picture of this species and the drivers of its nesting success and failure in a warming world.

An estimated global population of a mere 12,000-17,000 Black Oystercatchers rely completely on rocky islets and outcrops, and intertidal mussel beds rich with shellfish and crustaceans, from Baja California north to the Aleutian Islands. With up to 6,000 of these shorebirds found in California and 600 in Oregon, the west coast south of the Columbia River is a key bastion of the species, yet almost nothing was known about their breeding success, known as “productivity,” a fundamental marker of the future of a species.

“Many people who have spent time along our coasts recognize this chatty, charismatic bird with its bright orange beak against jet black feathers,” said Dan Orr, Director of Geospatial Science at Audubon California and a co-author of the study. “But there was a huge lack of data about these shorebirds on the west coast, despite their small global population.”

Observers trained by state and federal biologists conducted an average of 13 weekly surveys during breeding season, following each pair’s nest effort to completion and noting numerous variables including nest location, nest height above water, and disturbances from people, dogs, and other wildlife. Though it was previously known that Black Oystercatchers occupied a narrow band of rocky intertidal habitat, the findings showed ideal nesting conditions to be more specific: high up onshore or high up on an offshore rock.

"I'm proud that we produced information that will help us protect this beloved species as their intertidal world changes,” said Anna Weinstein, lead author, former Audubon staffer, and Senior Project Manager at Solano Land Trust. “They are tough birds, long-lived, choosing to nest near adequate food for chicks, and often seen driving away would-be predators from nests. This gives me a lot of hope they can survive and thrive - and thrill generations of coastal visitors - until we can dramatically reduce emissions and stabilize the climate."

The study illuminated that nesting too low in their preferred habitat leaves chicks vulnerable to high surf and storms, while nesting onshore exposes them to predation or human interference. With sea levels in California predicted to rise between one-half to three meters by 2100, and other accelerating climate threats, such as extreme storms, climate change can severely limit available habitat and further disrupt the species’ ability to reproduce.

“Black Oystercatchers literally live on the edge, relying exclusively on the thin band of intertidal habitat on our coasts,” said Ryan Carle, study co-author and Science Director of Oikonos Ecosystem Knowledge. “This study highlights the vulnerability of this unique intertidal habitat and the iconic Black Oystercatcher, to both climate change and human disturbance.” 

The study found that the iconic marine shorebird is stable in the more northern parts of California and in Oregon, and far less stable south of Point Reyes, where disturbance may be greater. The result of a trusted partnership between the Audubon network and state and federal agencies that manage key areas for birds, including state marine reserves and the CA Coastal National Monument, the study also identified the best types of nest habitats, helping to focus conservation and community stewardship efforts.

“The contribution of Oregon nest data to this study was critical in expanding the regional scope of the effort and enabled documentation of the striking gradient of increasingly higher nesting success from south to north” said Joe Liebezeit, co-author and Assistant Director of Statewide Conservation at Bird Alliance of Oregon (formerly Portland Audubon).  

The success of the study relied on the long-term dedication and monitoring of hundreds of volunteer researchers (“community scientists”) along the coast, including from the Mendocino Coast, Madrone, Golden Gate, Marin, and Monterey Audubon chapters in California; State Parks volunteers in San Luis Obispo County; and Bird Alliance and Audubon members across the Oregon coast. These observers also served as coastal stewards, teaching thousands of visitors about Black Oystercatchers and their rocky intertidal home.

“Community science was key here - almost 200 passionate volunteers devoted thousands of hours monitoring nests during breeding season,” said Jodi Isaacs, Environmental Scientist with California State Parks San Luis Obispo Coast District. “Community science projects like this can be critical to successful long-term monitoring, giving us really valuable insights into how bird populations are doing and what sorts of conservation and management efforts may be needed to help them.”

The report highlights the need for continued monitoring and focused stewardship of ideal nest sites, including high offshore islands near mussel beds, and feeding areas that could help support Oystercatchers as their ocean environment changes. Marine reserves, the California Coastal Monument, and other protected areas also assume increased importance as the birds lose habitat. 

 

#  #  # 

Media contacts:   

Shineh Rhee/Audubon California:

shineh.rhee@audubon.org 

415.644.4605 

About Audubon
The National Audubon Society protects birds and the places they need, today and tomorrow. Audubon works throughout the Americas using science, advocacy, education, and on-the-ground conservation. State programs, nature centers, chapters, and partners give Audubon an unparalleled wingspan that reaches millions of people each year to inform, inspire, and unite diverse communities in conservation action. A nonprofit conservation organization since 1905, Audubon believes in a world in which people and wildlife thrive.