We analyzed patterns of abundance and distribution of wintering waterbirds in Tomales Bay, California, based on 21 baywide winter surveys over 7 years from 1989-90 to 1995-96. Total waterbird abundances averaged 21,943 (min. = 14,842, max. = 25,553), excluding shorebirds and gulls. Mean waterbird density was 770 birds/km2 with the greatest concentrations along the east shore and in the area of the Bay between Pelican Point and Tom’s Point. Surf Scoter, Bufflehead, and Greater Scaup together accounted for 70% of the total waterbirds. Aerial count data from the U. S.