Restoring oyster-reef habitat critical to conservation of this threatened shorebird species.
When homeowners owe more on their home loan than what the house is worth, their mortgage is considered underwater. This can create a number of financial problems for the homeowner. Recently, a threatened Florida shorebird species’ habitat began slipping underwater in a different, but no less troubling, way. Each year, the second-largest wintering U.S. population of American oystercatchers flocks to Florida’s Big Bend region, with most of the birds gathering in Dixie, Levy and north Citrus counties along the Gulf of Mexico. These shorebirds depend on the oyster reefs here for food and shelter critical to their winter survival. But recent declines in available oyster reef habitat created concerns about the future of the American oystercatcher, which already has a small and declining population. This prompted FWRI researchers to find out which oyster reefs are most beneficial to the shorebirds and what part of the reef they are using to help managers determine how and where to focus restoration efforts.
In 2011, FWRI researchers and a partner at the University of Florida began the first phase of the study – conducting field work from November to March when American oystercatchers are wintering in the Big Bend region. They observed the birds’ habitat use and movement patterns, and documented food availability and what American oystercatchers ate. Researchers paid very close attention to the birds’ habitat selection and recorded detailed descriptions of the oyster reefs, including distance from shore, elevation above the water and percentage of vegetation and oysters present. They also noted how American oystercatchers use these oyster reefs during different environmental conditions, including height of tide, wind strength and wave action.
Researchers learned American oystercatchers use oyster reefs closer to shore as feeding grounds, while reefs further from the shoreline provide a place to roost, or rest, and avoid predators. Despite the decline of oyster reef availability, food resources are not currently an issue for American oystercatchers. These shorebirds are primarily threatened by the lack of roost sites during high-tide. Not only are these oyster-reef roost sites scarce during high tide, but erosion and sea level rise are further reducing their availability. Researchers concluded that preserving and improving these high-tide roost sites and potentially constructing new roosting habitat should help American oystercatchers survive the winter.
In the second phase of this study, researchers will collaborate with land managers, local oyster harvesters and scientists who study oysters to implement a restoration plan. They will then monitor how American oystercatchers respond to learn whether more and enhanced roosting habitat improves the shorebirds’ winter survival. If so, this habitat restoration strategy can be applied at other locations to help the Big Bend wintering population of American oystercatchers begin to increase.