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ARAMBURU ISLAND ENHANCEMENT PROJECT

Autumn update on Aramburu Island restoration

We have had a busy summer on Aramburu Island. Over the past several months, we’ve made much progress on the island. Audubon (1) completed pre-restoration shorebird monitoring, (2) completed pre-restoration terrestrial land bird surveys on the island, (3) maintained native grasses in our nursery for island revegetation, (4) collected native plant seeds to plant next winter, (5) relocated the native oyster population on the island, and (6) began and completed shoreline construction.

Audubon completed the pre-restoration shorebird surveys on Aramburu and Pickleweed Islands. Shorebird surveys began in September 2009 and were completed in August 2011, providing us with 2 years of pre-restoration shorebird data. We also completed terrestrial land bird surveys in August 2011. These data will be used to assess shorebird and songbird response to restoration by comparing the number of shorebirds and songbirds detected before and after restoration relative to the control site, Pickleweed Island. Pre-restoration shorebird surveys showed that few shorebirds used Aramburu Island. We detected 88% more shorebirds using Pickleweed Island during low tide than Aramburu Island and 91% more shorebirds at high tide. In 2011, we detected 44 species on the Aramburu’s upland and 29 species on Unnamed and Pickleweed Islands. Species detected on Aramburu but not on the control islands include Anna’s Hummingbird (Calypte anna), Bewick’s Wren (Thryomanes bewickii), Bushtit (Psaltriparus minimus), Osprey (Padion haliaetus), White-tailed Kite (Elanus leucurus), and American Crow (Corvus brachyrhynchos), which typically prefer shrubbier habitats with tall perches that are available on Aramburu but not on the control islands. Species observed breeding on Aramburu include Canada Goose (Branta canadensis), Song Sparrow (Melospiza melodia), and Black-necked Stilt (Himantopus mexicanus). Species likely breeding on Pickleweed include Canada Goose and Song Sparrow.

In preparation for revegetation on the Island we also collected native plant seeds from the Island to be planted after construction. The native grasses in the propagation beds are doing well and staff and volunteers have been maintaining and caring for them.

Several volunteers and staff relocated the native oyster population on Aramburu Island prior to construction activities because rebuilding the beach would have smothered the oysters. We took rocks containing oysters and placed them in the boat and drove them to the shores of the Audubon Sanctuary for safe keeping until restoration is finished. After the sandy foreshore is constructed next year, we will return the native oysters to Aramburu Island and build oyster mounds to attract additional oysters to settle along the intertidal zone.

On 8 August 2011 restoration activities began. Equipment and material were brought to the island by barge. Crews first removed non-native species on top of the eroded scarp along the shoreline and then smoothed out the surface to create a gentle sloping shoreline. After the shoreline was smoothed to the correct elevation, a combination of cobble, pebbles, sand, and oyster-shell hash were added to the shoreline profile. The larger cobbles were placed in the southern cell which receives greater wind-wave energy to create a more stable shoreline. Crews placed smaller material in the central and southern cells and let the waves rework the material to create a natural oyster-shell and sand beach. Large pieces of eucalyptus logs were placed along the shoreline to create micro-groins aimed at preventing longshore drift of beach materials. The large-woody debris was anchored down into the beach and pinned with metal stakes to ensure that the woody debris stays in place along the beach. Audubon California and project partners completed the restoration of 1.86 acres of shoreline on Aramburu Island on 16 August 2011. The shoreline improvements are dramatic and shorebirds began to use the new oyster-shell beach almost immediately. Within one day of placement of oyster-shell hash on the shoreline we observed 40-50 least sandpipers roosting on the beach. Before and after photos show the vastly improved shoreline.

Due to increased project costs, we phased restoration over two years. This year we completed the rock-sand beach and next year we will complete the sandy foreshore and the upland terrace restorations.

Project Background

Aramburu Island has been largely overrun with nonnative, invasive plants that don’t provide good habitat or food resources for the wildlife in Richardson Bay. Many of these nonnative plants form thick stands of a single species, like the French broom and Harding grass shown here.

In November 2007, the Cosco-Busan oil tanker hit into the Bay Bridge, spilling 58,000 gallons of oil into San Francisco Bay.  In the weeks following that disaster, Audubon was checking the shorelines of Richardson Bay twice a day to rescue oiled and sick birds, and to remove those that perished.  As a result, Audubon discovered that most of the birds ended up on Aramburu, a 17-acre island in the northwest region of Richardson Bay.  This crisis highlighted just how important this island is for wildlife.  Fortunately, Aramburu Island is owned by Marin County and managed by Marin County Parks and Open Space, who set it aside as a preserve in 1997.

As of 1985, more than 90% of the wetland acreage in the San Francisco Bay Region has been converted to other uses (San Francisco Estuary Project).  The remaining wetland areas are therefore critical for birds and other wildlife in the Bay, which is why it is very important to ensure the remaining wetlands and undeveloped areas provide high quality habitat for wildlife. Since the oil spill, Audubon has been researching ways to improve the island as habitat for birds and other wildlife. Unfortunately, the island has been largely overrun with nonnative, invasive plants that don’t provide good habitat or food resources for the wildlife in Richardson Bay, and the margins of the island are being eroded. We’d like to change that.

The Richardson Bay Audubon Center has partnered with Marin County to improve the habitat on Aramburu Island.  Audubon, with the help of a local consulting firm that specializes in wetlandsrestoration, Wetlands and Water Resources, iscurrently working on aconceptual habitatenhancement plan for the island. This work is funded by TogetherGreen, a partnership between Toyota and the National Audubon Society, and the Bechtel Foundation. 

Project Objectives
1. Rehabilitate existing tidal marsh and grassland habitats across the island, rehabilitate tidal flat and shoreline habitats along the eastern and northeastern borders of Aramburu Island, and establish gradual transition zones (ecotones) that support diverse native vegetation and optimum wildlife habitats for shorebirds, waterfowl, marine mammals, and native plant species.

2. Expand existing sand and gravel spit areas as shorebird roosting habitats and reduce wave erosion and shoreline retreat along the eastern and northeastern borders of Aramburu Island by selective placement (replenishment) of bay sand and gravel beach sediments with appropriate grain sizes for Richardson Bay wave energy.

3. Maintain topographic heterogeneity on the island to facilitate gradual movement of wetland habitats during sea level rise. 

4. Establish additional roost habitat for herons and egrets by placement of persistent large woody debris in storm drift-lines on the eastern and northeastern areas of Aramburu Island, and creating snags on the island.

The project will contribute to several of the regional restoration goals as outlined in the San Francisco Baylands Ecosystem Habitat Goals Report.  This report specifically identified the following objectives for Richardson Bay and the Strawberry Spit area:

• Protect and enhance harbor seal haul-out sites at Strawberry Spit.
• Restore and enhance tidal marsh.
• Restore and enhance fringing marsh for Point Reyes bird’s beak along the northwest edge of Richardson Bay.
• Restore high marsh near populations of rare and uncommon salt marsh plants to enable their expansion.

Project Timeline

The current project timeline is as follows:

Spring 2010: Complete feasibility analysis and draft conceptual enhancement plan

Late Winter 2011: Complete final conceptual enhancement plant

Late Winter 2011: Submit permits

Spring 2011: Complete CEQA analysis

Spring 2011: Complete the final design enhancement plans

August-October 2011: Phase I on-the-ground enhancement work

July-October 2012: Phase II on-the ground enhancement work

December 2012: Begin post-enhancement biological monitoring

For more information
Please stay tuned to this website for more information about the project and about community meetings.  If you’d like to get involved in volunteer activities related to this project, or if you would like to submit comments, please contact , Bay Ecologist.