Brooks Island is a naturally-formed, 373-acre patch of dry land in the east San Francisco Bay, about 10 miles northeast of the city of San Francisco. A breakwater sand spit of emplaced dredged material has become important nesting habitat for terns and gulls. Brooks Island is owned by the East Bay Regional Park District, which manages the island as a regional preserve for the protection of natural resources. Visitation to the island is by reservation only during the non-bird nesting season. Access to the island is by kayak only. The San Francisco Bay Bird Observatory and the Cypress Grove Research Station have been conducting long-term bird research on Brooks Island's breeding water birds.
Updated December 2008
Brooks Island supports over 18 species of breeding birds. The Brooks Island sand spit supports one of the largest breeding colonies of Caspian Tern in California, with 900 pair in 1998. 825 pair of nesting Caspian Terns and 243 California Gulls were documented in 2002 (SFBBO). Aside from this distinction, there was a sizable heron rookery here, which consisted of primarily of Black-crowned Night-Heron (maximum 100 pair) and Snowy Egret (maximum 95 pair), with a handful each of Great Blue Heron and Great Egret. This was apparently abandoned in the 1996, coinciding with the two-month appearance of a single Red Fox on the island (John Kelly, via email). In winter, the waters around Brooks Island support exceptional concentrations of certain inshore sea ducks and hundreds of shorebirds roost on the island during migration and winter (especially Western Sandpiper, Dunlin, Willet and Black-bellied Plover).
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Brooks Island is adjacent to Richmond Harbor where high levels of DDT have been detected. San Francisco Bay Bird Observatory in collaboration with US Fish & Wildlife Service Environmental Contaminants Division, collected eggs and monitored hatching success of Caspian Terns. Preliminary data from the study showed mercury above the 0.5 ppm level know to adversely affect bird reproduction. Vegetation is dominated by non-native ice plant in the Caspian Tern nesting area. Dredging by the Army Corps of Engineers needs to be scheduled outside the bird breeding season. Rodent and feral animal predation may be an issue for birds nesting on the island. The occasional recreational kayaker ignoring the signs prohibiting approach by boat has caused major disturbance to the tern colony during the breeding season.
It is managed by the East Bay Regional Park District, and may be visited only by kayak.
Brooks Island is a naturally-formed, 373-acre patch of dry land in the east San Francisco Bay.