BLACK OYSTERCATCHER NESTS SUCCESS WITH CALIFORNIA LEAST TERNS IN THE SAN FRANCISCO BAY

David Riensche; East Bay Regional Park District; driensche@ebparks.org; BEN PEARL, SUSAN RAMOS

“Tern Town”, located along the eastern side of the San Francisco Bay, provides island nesting habitat for three special status species. Since 2015, and for a total of six breeding seasons, the endangered California Least Tern (Sternula antillarum browni), the threatened Western Snowy Plover (Charadrius alexandrinus nivosus) and species of special concern the Black Skimmer (Rynchops niger) have nested successfully, in association with American Avocet (Recurvirostra americana) and Black-necked Stilt (Himantopus mexicanus). On June 6, 2022 the Black Oystercatcher (Haematopus bachmani) which is uncommon within its range and is typically limited to the rocky intertidal established a nest, on the island. Black Oystercatchers have been documented nesting near gulls and terns (Sterna spp.) and are known to use their bills to jab at other species chicks that wander into their territory. We witnessed no such incident, and this is the first documented occurrence of oystercatchers successfully nesting and fledgling young with California Least Terns. Diet trend data showed the oystercatchers forage on, in decreasing order of abundance: Japanese Little-necked Clam, Ribbed Mussel, and Bent-nose Clam, Limpets. This site-specific information on breeding Black Oystercatchers supports recovery plan tasks that are consistent with managing habitat for near California Least Tern, Western Snowy Plover and Black Skimmer.

Poster Session  InPerson Presentation