Tampa Harbor Dredging Provides Island Haven for Birds
Every year, hundreds of birds flock to two manmade islands at the edge of Tampa Harbor’s federal navigation channel in Hillsborough Bay. The birds have found the islands, which are posted and protected from trespassers, to provide ideal conditions to safely court, nest, and raise their young.
At the moment, though, more than just baby birds are being raised on one of the islands. Major construction is ongoing at Dredge Material Placement Facility (DMPF) 3-D to raise the dike there and crews are diligently working beside their avian companions.
Jacksonville District built the 400-acre island known as “3-D” as a dredge material disposal site between 1978 and 1982 while deepening the Tampa Harbor.
“This is the first dike-raising at 3-D since its original construction, and it’ll bring the dike from 23 feet to 40 feet to create about 15 million cubic yards of capacity,” project manager Milan Mora said. With that new capacity, he says 3-D will help sustain another 20 years of dredging for the Tampa Harbor Federal Navigation project.
Beneficial use of dredged materials is normally associated with shoreline protection or as fill for upland areas, but today there’s also another recognized value. Dredged material disposal islands such as 3-D create bird nesting habitat, even though that was not the original purpose.
Mora said the Corps plans to reduce the invasive vegetation that has grown on the island since its creation once the dike construction is completed March 2015. Species such as Australian pine, leadtree, cogon grass, and Brazilian pepper grow rapidly on the island, providing seed sources that spread to other areas in Tampa Bay, and posing some threat to the dike.
“Trees and their root systems can cause erosion on the dike, especially during storm events. We’re planting grass along the dike slopes to contain the compacted soils,” he said.
Native vegetation in areas not on the dike itself will serve some of the birds’ needs, while others prefer the sandy, un-vegetated areas that mimic beaches, said Aubree Hershorin, Ph.D., project biologist. She said that nesting had declined at 3-D in the past several years as birds selected the open landscape on the less vegetated disposal island located just north of 3-D.
The project team recognized during the planning process that clearing the island would make it very attractive to nesting shorebirds, Hershorin said, and the contractor would need to work through at least one shorebird nesting season. Extensive consultation occurred with project partners in the region to brainstorm methods for deterring birds and managing construction activities to prevent project shutdowns while avoiding impacts to nesting birds, as mandated by state and federal law.
The Tampa Bay Migratory Bird Protection Committee, which includes members from U.S. Fish and Wildlife Service, the Florida Department of Environmental Protection, Florida Fish and Wildlife Conservation Commission, Tampa Port Authority, and Audubon Florida, meets semi-annually to discuss upcoming dredging projects that may affect nesting shorebirds and actions to avoid impacting them at the two DMPF islands in Tampa Bay.
Hershorin said the ongoing work at 3-D is an example of managing construction in a positive way to prevent impacts to nesting birds while allowing construction activities to continue.
“The success of the DMPF as nesting habitat this spring is a direct result of the collaborative relationship we have with our partners in Tampa Bay,” Hershorin said. “It truly takes the whole team of agency personnel and NGOs [non-governmental organizations], along with a cooperative contractor, for nesting to be successful. We also rely heavily on the expertise of the Audubon Florida staff, who worked to monitor these islands since their construction and provide us with valuable information on the habits of the birds nesting here.”
“DMDF 3-D is a critical component of the Hillsborough Bay Important Bird Area, recognized for its global significance as extremely valuable habitat for birds by BirdLife International and the National Audubon Society. It is also on Audubon Florida’s list of Important Bird Areas of Florida, which lists the top 100 sites in Florida that are important for birds,” said Ann Paul, a regional coordinator with Audubon Florida.
To work in harmony with the island’s bird community, the current construction contractor, Carter’s Contracting Services, Inc., hired LG2 Environmental Solutions (LG2ES) to provide daily bird monitoring services.
Lorraine Margeson, one of the monitors, has been a volunteer bird advocate and surveyor for 12 years, focusing much of her efforts on shorebird, colonial wading bird, and grassland bird conservation efforts.
“LG2 did a great job in prepping the contractors with pertinent nesting bird information, including emphasizing recognition of the calls of the American Oystercatcher, a primary target for bird conservation and nesting potential on this project,” Margeson said.
Workers will complete the dike project in early spring 2015, just in time to avoid another nesting season. The Corps anticipates that during the life of the Tampa Harbor Federal Navigation project, numerous generations of birds will have hatched on 3-D.