On 13 comprehensive censuses of the San Francisco–San Pablo Bay estuary and associated wetlands, we counted 325,000–396,000 shorebirds (Charadrii) from mid-August to mid-September (fall) and in November (early winter); 225,000 from late January to February (late winter); and 589,000–932,000 in late April (spring). Twenty-three of the 38 species occurred on all fall, early-winter, and spring counts.