The American oystercatcher (Haematopus palliates), with its distinctive bright red bill and yellow eye, is state listed as threatened in Florida. Major threats to the oystercatcher include widespread habitat loss, increased anthropogenic pressure, and several effects of climate change, particularly sea-level rise. Oystercatchers migrate from northern Atlantic breeding sites to coastal wintering areas on both the South Atlantic US coast and the Gulf of Mexico. Two main, geographically separate winter aggregations of the eastern population exist, at Cape Romain, South Carolina, and in Florida’s Big Bend, also known as the “Nature Coast.” The Nature Coast been estimated to support more than 1,100 individuals from nearly all Atlantic coastal states during the winter. While considerable research has been focused on breeding habitat conditions, little has been devoted to understanding or improving wintering habitat. Florida Fish and Wildlife Research Institute researcher Janell Brush led this project to restore American oystercatcher wintering habitat near Cedar Key in the Big Bend area of the Gulf Coast of Florida.
In Florida’s Big Bend, intertidal reefs dominated by the eastern oyster have experienced a decline in area of 66 percent since the 1980s, a loss likely to have substantial wildlife impacts on reef-dependent wildlife. This study examined the use of oyster reefs by wintering American oystercatchers in this area. Crucial high-tide roosts were found to be away from all vegetation and limited in number; roosts were located on offshore oyster reef habitat, which has experienced an 88 percent decline in area over the past 30 years. These oyster communities are extremely sensitive to a variety of threats, including erosive wave action; contamination; overharvesting; and shifts in oxygen, salinity and turbidity. The oysters in this area are in decline due to the increasing length and frequency of low-freshwater discharge events which has led to poor recruitment and survival of oysters, erosion of oyster reefs, and, ultimately, irreversible loss of substrate appropriate for oyster settlement.
Considering the loss of offshore oyster reef habitat used as high tide roosts for the American Oystercatcher, the research team implemented a restoration strategy which included designing a structure that would buffer wave energy, encourage accretion and provide oyster settlement. Construction materials included large bagged blocks of living oysters, which are available locally in large numbers from damaged clam farming infrastructure associated with commercial clamming operations. These bags, filled with substrate and live oyster larvae, are removed from existing clam leases and placed on restoration sites to serve as a breakwater-barrier revetment hybrid which buffers wind-driven wave energy. Barriers like this stabilize the existing reef, prevent further erosion and increase elevation by promoting accretion. Limestone rock was placed behind the barrier to function as a larger hard structure for oysters to attach and grow. Loose shell was used to fill large undesirable gaps between pieces of limestone.
The sediment accretion zone behind the clam bags.
American Oystercatchers landing at the restoration site after being disturbed off an adjacent site.
American Oystercatchers using the restored reef.
Limestone on the restoration site.
Oyster growth on limestone.
Volunteers completing the last stage of the restoration by placing loose shell over the limestone.
This project is noteworthy in that it was the first oyster habitat restoration project specifically designed to benefit roosting American oystercatchers. The stabilized oyster reefs have successfully withstood several storms, including Hurricane Hermine. The ability of this design to show resistance to extreme weather conditions as well as observations of oyster resettlement is a good indicator that oystercatcher roosting habitat will be improved following restoration. Additionally, researchers estimated annual and winter survival and site fidelity for the population of American oystercatchers using the Nature Coast region of Florida. This study provides the first broad-temporal scale estimates of annual survival for wintering American oystercatchers. Results will be published in fall 2018.
Janell Brush and her team have already identified additional reefs in the Cedar Key area to target for restoration, after the success of this first project. “The resiliency of this project to storms can not only be a model for American oystercatcher habitat restoration, but other restoration projects with similar goals and objectives,” Brush said. The team hopes that this project encourages and informs more targeted restoration activities to directly benefit birds. Currently, there are hundreds of restoration projects being considered for funding over the next 15 years. Careful thought needs to go into the restoration project prioritization process, restoration project design and planning to determine the cost/benefit analysis of the project for birds, as well as feasibility and sustainability of the project. Long-term project monitoring is imperative to determine project success, and in some cases management is necessary to ensure the habitat remains suitable for birds over time. Restoration projects that are implemented in the adaptive management framework provide valuable information to inform future restoration projects.
This project was implemented by the Avian Research subsection staff out of the FWRI Lovett E. Williams Jr. Wildlife Research Lab in Gainesville, FL and was funded through a National Fish and Wildlife Foundation Shell Grant.