Scientists surveying rocky islands this week off the Mendocino County coast within the California Coastal National Monument made a remarkable discovery – several breeding sites for the Ashy Storm-Petrel, a rare and declining seabird not reported nesting in this area since 1926. The U.S. Fish and Wildlife Service estimates that there may be as few as 5,500 smoky-gray Ashy Storm-Petrels in the world. Nearly all of the robin-sized birds breed on the Channel Islands off southern California and the Farallon Islands off San Francisco, with a handful of much smaller colonies known between Bird Rock (Marin County) and the Todos Santos Islands off Ensenada just south of the U.S.-Mexico border. (photo by Glen Tepke)
“This shows that Ashy Storm-Petrels still persist in the northern part of their range, and at more sites than had been known,” said Harry Carter, from the seabird research organization California Institute of Environmental Studies. “It may increase the bird’s resiliency to known threats in other areas such as oil spills, light pollution, predation by invasive predators, and more. It also means we have a responsibility to protect and monitor these sites with their own unique breeding conditions and conservation issues.”
Ashy Storm-petrel is a candidate for listing under the federal Endangered Species Act, with a decision from the federal government expected next year. The discovery expands the current breeding range of the species north by about 13-15 percent, a finding that has important implications for the conservation of the species.
Carter is one of the world’s top experts on the species, and he led the survey team with Mike Parker and Josh Koepke. The team found breeding birds, which nest in rock crevices, on one historic colony site that was thought to be extirpated, and on three new sites. These sites may harbor 100 or more breeding individuals and additional birds likely breed nearby in inaccessible locations, which is significant given the small global population.
“Searching for Ashy Storm-Petrels on these rocks is tough and dangerous work, and we are grateful to these biologists for shining light on an elusive species that is a high conservation priority for many state and federal agencies and conservation groups,” said Audubon California’s Anna Weinstein. “And, the state’s new suite of marine protected areas will help to support food resources for Ashy Storm-Petrels provisioning their young at these sites.” The research was funded by the National Fish and Wildlife Foundation’s Pacific Seabird Program, a Pacific-wide conservation initiative established in 2011 for which Ashy Storm-Petrel serves as one of ten priority species.