Black Oystercatcher Monitoring and MCAS Involvement


Perhaps you didn’t know that Morro Coast Audubon invests in research and monitoring of birds in our area. In addition to the Breeding Bird Survey at Sweet Springs, the Shorebird Survey, and Brown Pelican Survey, MCAS has funded the collection and collation of data and the final write-up of monitoring the breeding success of the Black Oystercatcher in San Luis Obispo County.

The Black Oystercatcher (Haematopus bachmani) is a large, long-lived shorebird that inhabits rocky intertidal zones along the West coast of North America. Black Oystercatchers forage primarily on intertidal macroinvertebrates such as mussels and limpets. Pairs in California nest primarily on rocky outcrops, but may also select mainland sites against or near the faces of bluffs and cliffs. They are considered an indicator species, reflecting the health of rocky intertidal ecosystems that comprise portions of the continent’s Western coast.

Starting in 2012, Audubon California orchestrated a collaborative effort to assess the reproductive success of Black Oystercatchers by coordinating with local Audubon chapters, the U.S. Fish and Wildlife Service, the U.S. Bureau of Land Management (BLM)-California Coastal National Monument, California State Parks, and other interested groups to conduct nest monitoring surveys from May through September. An initial 5-year program blossomed to a 10-year data collection effort.

Monitoring efforts for the 2020 and 2021 breeding seasons in San Luis Obispo County have been and will be conducted by community scientists and State Park employees. Efforts were coordinated by Jodi Isaacs, an Environmental Scientist for California State Parks. For the last two years of monitoring, Morro Coast Audubon Society provided funds for a Seasonal State Park Employee to augment volunteer monitoring efforts, collate all the data, and write up the annual report.

Data collected include the nest stage, behavior of the adults, number and stage of eggs, number and age of chicks, the presence of predators, and disturbances to nesting oystercatchers. After a nest location was established, nests were monitored at least once a week for a minimum of 30 minutes. If a nest failed early in the season, a monitor would continue to survey the site in subsequent weeks to confirm nest failure and check for re-nesting attempts. In instances where a nest was not discovered until after hatching, the chicks were monitored weekly until they either fledged or failed to fledge. Fledging of chicks is confirmed by observing flying or if the chicks reached 36 days after their hatch date.

2020 Annual Report