As part of an All Taxa Biodiversity Inventory (ATBI) for Tomales Bay, California, we analyzed 13 years of standardized shorebird and waterbird survey data, the results of numerous published and unpublished reports, and verified anecdotal documentation of bird species occurrences in Tomales Bay.

A comprehensive list of bird species, keyed by taxonomic hierarchy, seasonality, special status categories, preferred habitats, relative abundance, and occurrence within sub-areas, indicates 163 species known to occur or have occurred in Tomales Bay below the mean higher high tide level. These include 122 species that occur regularly or occasionally and 41 species that occur only rarely with less than five documented occurrences. Species normally associated with adjacent habitats were included only if their presence was considered to indicate use of suitable habitats in Tomales Bay. Based on species occurrences in other areas along the Pacific Coast, we predicted that the following undetected species are likely to be found on Tomales Bay: Arctic Loon (Gavia arctica), Northern Fulmar (Fulmaris glacialis), Steller’s Eider (Polysticta stelleri), Wilson’s Phalarope (Phalaropus tricolor), and Sabine’s Gull (Xema sabini).

We also recommended specific protocols for shorebird and waterbird surveys. Analysis of randomized species accumulation curves suggested that optimal efficiency for detecting species (but not necessarily species abundances) can be achieved by conducting 20-35 baywide winter waterbird surveys over a period of five years; a minimum of 20 baywide counts of wintering shorebirds over five years; and a minimum of 20 baywide shorebird counts each during the fall and spring migration periods over at least five years.

A bibliography of relevant literature on birds of Tomales Bay is included in the report. The Cypress Grove Research Center of Audubon Canyon Ranch, in Marshall, CA, conducts ongoing shorebird and waterbird monitoring programs on Tomales Bay.