Oystercatchers—in their black, waterproof suits, pink tights, and bright orange bills and eye rings—are finding a new oyster reef in San Rafael built by the California Coastal Conservancy and partners in 2012 much to their liking. The reef offers a smorgasbord of delicious oysters and all kinds of other invertebrates, says U.S. Geological Survey’s Susan De La Cruz, who is monitoring birds and benthic invertebrates for the Conservancy. “The [bird] species that’s certainly responded the most is oystercatchers,” she says.
Oystercatchers feed on shellfish, mussels, clams, sea urchins, starfish, worms, and—of course— oysters. Oystercatchers use their long knife-like bills to seize the shellfish before they can close up. When the oystercatchers find a partially open clam or oyster, they stab their bills into the shell and cut the muscle that clamps the shells shut. Once in a while this can backfire: an oystercatcher can drown if a tightly rooted mussel closes down on its bill and prevents the bird from getting away when the tide comes in. 
Oystercatchers also feed by taking loose shellfish out of the water and pounding away at the shell to find the animal inside. They also probe down into the mud with their long bills to find buried clams, like shorebirds do.
Oystercatchers were present at the Marin study site in pre-project surveys, foraging in shoreline riprap, De La Cruz says, but during the same time period post-project, the researchers found that the mean number of birds within the survey area had significantly increased, and that the birds are using the oyster reef. “The cool part is that the Marin Islands are a nesting site for them—and those birds are likely coming over and foraging on the oyster reef. The increased food availability could be beneficial to these birds during the nesting season,” says De La Cruz.
Oystercatchers can use all the help they can get. In San Francisco Bay, though they have expanded their range, many of their nesting sites have failed in the past few years, says Audubon California’s Anna Weinstein. 
Nests overall do not fare that well in the Bay, she says, probably because of disturbances from people, predators like Western gulls, and boats that flush them from their nests. “[The Bay is] not ideal for nesting,” says Weinstein. “They’re really more of a coastal bird.” But in the winter, the Bay provides a very important sheltering area for them where they can rest—and gorge on all the oysters they can eat.
According to the Conservancy’s Marilyn Latta, more than two million native oysters have settled at the San Rafael site, along with juvenile Dungeness crabs, bay shrimp, white sturgeon, and a diversity of other fish, birds, and wildlife.
To learn more about native oyster restoration in San Francisco Bay, click here.
Read about The Watershed Project’s native oyster restoration project at Point Pinole here.
Photo credits: Jerry Ting (top)
