 The marsh is a productive estuarine ecosystem providing habitat for a wide diversity of flora and fauna, including numerous rare and endangered species such as the California clapper rail and California freshwater shrimp.Because of its rich avafaunal content, the Napa Sonoma Marsh is one of only seven marshes selected for intensive study by the Point Reyes Bird Observatory (based on a total of 50 discrete marshes appurtenant to the San Francisco Bay).Around 1860, the Napa Sonoma Marsh was one of the most productive wetlands of the Pacific Coast, providing habitat for millions of birds.