In June, the California Audubon Society set out to do something no other organization has. With clipboards, binoculars and GPS devices, volunteers hit the rocky coastlines to survey the native black oystercatcher. “Although it’s a focal species for the Fish & Wildlife Service and you see its picture everywhere, very little is known about the bird,” says Anna Weinstein, Audubon California’s Seabird Conservation Coordinator and head of the survey.
With its black plumage, vibrant orange-red bill and fiery eyes, the black oystercatcher is a showy sight on the coast between Southern California and Canada. Despite the misleading name, it only lives near oyster beds—it doesn’t feed on them. Instead, it snacks on a broad diet of other marine invertebrates like limpets, making it a great indicator for the success of intertidal zones, which have a great impact on the ecosystem as a whole.
Previously, there was only a global estimate of about 11,000 individual oystercatchers, with approximately 1,000 living in California. The census revealed good news.
“The survey results were quite surprising,” Weinstein says. Volunteers from Orange County to the Oregon border covered an estimated 9 percent of California’s coastline (about 20 percent of the oystercatcher’s habitat) and spotted 1,346 individuals and 175 nests. “The nesting success was shocking,” says Weinstein. “Perfect nests of a certain size and shape were discovered.”
This fledgling success is due to the oystercatcher’s habitat preference. Unlike marine birds that nest on beaches, where predators or humans can disturb them, the oystercatcher’s love of rocky cliffs and intertidal geography allows for perfect camouflage. Because of this, the Audubon Society thinks the species could be doing even better than the survey suggests.
However, this doesn’t mean that the black oystercatcher has flown from danger. Natural predators like raccoons and possums brave the rocks to feast upon eggs, and while Weinstein doesn’t believe that humans are the biggest threat to the bird, she does acknowledge that seaweed harvesters and abalone divers can cause problems by disturbing nests and depleting food supplies. Oystercatchers are also extremely vulnerable to climate change, with rising sea levels and ocean acidification having already pushed them farther north than expected. “They’re tough and they know how to make it in the world,” Weinstein concludes, “but their world is changing fast.”
