Nesting Observed on Yosemite Slough Bird Island

by Giselle Goulette

Working with the California State Parks Foundation, WRA designed a nesting bird island that was incorporated in the restoration of Yosemite Slough, a major wetlands restoration and park development project in southeastern San Francisco.  For the first time since the project’s first phase of restoration was completed in 2012, local shorebirds are using the island for summer nesting.

Nesting Vital to Habitat Restoration

American avocet nest observed on Yosemite Slough's nesting island

American avocet nest observed on Yosemite Slough’s nesting island

American avocets have established five nests on the created nesting island installed as part of the tidal marsh restoration at Yosemite Slough.  The nests were observed during annual habitat establishment monitoring at the site in 2015, approximately three years after construction of the restored marsh.  The bird island consists of a thick layer of sand surrounded by adjacent marsh.  The sand layer excludes marsh vegetation, providing a relatively barren nesting area along the shoreline preferred as nesting habitat for shorebirds.

The sand island was designed to provide nesting habitat for summer nesting shorebirds, including American avocets.  Isolation of the island from the mainland by tidal channels provides protection from animals and human disturbance.  Adjacent restored tidal marsh vegetation and mud flats provides foraging habitat for migratory and resident birds.

About Yosemite Slough

The Yosemite Slough tidal restoration and public park project is within California State Parks Candlestick Point State Recreation Area and adjacent to a tidal channel referred to as Yosemite Slough.  The slough is located just north of the San Francisco county line on the western shore of the South San Francisco Bay in San Francisco’s Bayview-Hunters Point neighborhood.

WRA rendering of planned Phase 2 improvements

WRA rendering of planned Phase 2 improvements

The restoration design for the project included restoring 10 acres of historic bay fill to a functioning tidal marsh in an industrial area along the San Francisco Bay margin.  In addition to the marsh restoration and the bird island, design elements included nursery areas for fish and benthic (bottom dwelling) organisms and a new portion of the San Francisco Bay Trail.  The project also addressed soil contaminant issues arising from previous fill activities and industrial land use.Phase 1 of the project, which included the tidal marsh restoration and Bay Trail construction, was completed in 2012.  This work was recognized by the San Francisco Estuary Partnership’s Outstanding Environmental Projects.  Future project phases for the remainder of the 34-acre site include the integration of proposed transitional and upland areas to buffer sensitive habitats and passive public use areas with an environmental interpretive center.

Conclusion

The occurrence of nests on the bird island shows a progression of the developing habitat on the site with increasing complexity to support a variety of local bird species.  The project is a successful example of integration of both restoration and public use in an urban context, balancing wildlife needs and human access.

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