Unique collaboration monitors black oystercatchers on local rocky shores.

A raven-sized bird with a bright orange beak pipes out a whistle, then flies into the surf at Point Pinos in Pacific Grove. Within seconds, a nearly identical bird swoops in and takes its place in the tidal tumbles of granite.

Hugo Ceja peers through a telescope he’s set up on a large, flat rock nearby. He invites me to take a closer look at the bird, which has settled into stillness, and pay close attention to the irregular shape of its orange-ringed pupil. That eye fleck, Ceja says, means this oystercatcher is a female. She’s just taken over the job of incubating her two eggs, relieving her mate to hunt for mussels.

Ceja has help today from citizen-scientists Stephanie Edenholm, Mary Dainton and Sue Addleman. Together, they’re gathering data on the little-known shorebird to help wildlife managers figure out how to ensure their long-term survival.

What scientists do know: Black oystercatchers live along the North American West Coast from Alaska’s Aleutian Islands to the Baja Peninsula, but only in very specific rocky intertidal habitats. Along the Monterey Bay shoreline, Pacific Grove to Big Sur is prime oystercatcher real estate.

Despite their name, they don’t catch oysters around here. Instead they go for snacks like mussels, limpets, clams, small crabs and peanut worms.

Biologists once estimated there were fewer than 900 black oystercatchers along the California coast, but a 2011 Audubon survey came up with a population closer to 5,000. In 2012 Audubon and its collaborators, including the BLM’s California Coastal National Monument, launched a statewide monitoring effort to learn more.

Ceja, a recent CSU Monterey Bay graduate, and retired BLM manager Rick Hanks are coordinating the Central Coast volunteers, whom they recruited from the Pacific Grove Museum of Natural History and Point Lobos State Natural Reserve.

It’s an example of the citizen science that’s become a hallmark of Monterey Peninsula culture. Similar volunteer-driven initiatives sample pollution runoff into Monterey Bay after the season’s first rain, test trees for signs of sudden oak death infection, track sea otter movement, monitor the health of underwater reefs, count harbor seal births and observe tiny beach-spawning fish called grunions.

The oystercatcher program is now in its fourth year, with six more to go. Each week, more than 30 volunteers lug scopes and data sheets to check on 34 nests from Hopkins Marine Station to Point Lobos.

It’s not always easy to spot the birds along the foggy shoreline. “You have to get your oystercatcher eyes,” Dainton says. “It could be a crow, a rock or even a shadow.”

“Look for the carrot,” Edenholm adds, referring to the bird’s long orange beak.

Or listen for their call: Ceja demonstrates with a staccato whistle.

The two pairs we’re watching today, MP4 and MP5, maintain an invisible boundary along the rocks. “Not too many birds are territorial the way these guys are,” Ceja says. “They’ll greet each other and do a little dance. They’re negotiating the line.”

Oystercatcher couples make their scrappy, pebbled nests along the shoreline, laying two or three eggs in May. The chicks hatch about a month later. On June 2, volunteers reported the season’s first two hatchlings near Hopkins.

Ceja squints at MP5, the pair we’re observing. They’re experienced parents, he says, so he’s a little concerned they only laid two of their brown speckled eggs instead of a more optimistic three.

Many birds are born featherless and blind, but black oystercatchers hatch with downy feathers and start walking within hours. They take 35-40 days to fledge, then stick with their parents for three to nine more months.

Once their parents kick them out, they form juvenile packs that roam, like teenagers at Northridge Mall, until they reach adulthood around age 5. Once they find a mate, they usually mate for life (and life can be as long as 15 years).

Then they claim a territory and attempt to raise chicks. The odds are against them: Last year, only 15-19 percent of oystercatcher eggs in the Central Coast monitoring program survived to fledging, Ceja says.

The survival rate was even lower, 6-8 percent, in the touristy areas between P.G. and Asilomar. If adult oystercatchers feel threatened by people or dogs, he says, they might leave their eggs vulnerable to predators like gulls and crows.

Ropes and signs mark the oystercatcher nests at Point Pinos, asking beachwalkers to give the wildlife some space. But even without signage, Ceja says, people can learn to read their cues.

“If you ever see a bird flying close and making noise,” he says, “it’s because you’re too close.”