Baptiste Collette Bayou

Venice, Louisiana, United States

Applying an innovative adaptive management approach. Dating to the late 1860s, Baptiste Collette Bayou was a small canal between the Mississippi River and Breton Island Sound. The bayou’s natural subdelta, once covering up to 52 square kilometers, began to deteriorate in the 1950s due to subsidence and ponding. Federal interest in Baptiste Collette as a navigation route grew during this period and led Congress to authorize channel improvements that began in the early 1970s, when dredging enabled the channel to be used as an alternate route for the Gulf Intracoastal Waterway (GIWW). Material dredged from the channel was used to restore degraded wetlands. By 1977, this practice was expanded to include construction of bird nesting islands. Today, sediment from maintenance of the Baptiste Collette Bayou channel is placed in shallow, open water suitable for nesting seabird colonies on either side of the channel. This unconfined placement creates a wetland habitat adjacent to the waterway’s jettied entrance and the islands seaward of the jetties. Created habitats include marsh, scrub-shrub, bare land, and beach. Using dredged sediment to create or restore coastal habitat has become the current state of the practice in the U.S. Army Corps of Engineers, Mississippi Valley Division, New Orleans District (CEMVN) Navigation Program.

Article Cover: Gunn Island in late July 2021 showing dominant growth of Phragmites during that year’s breeding season. (Photo by Jake Jung)

Producing Efficiencies

The bird islands were constructed with dredged sediment with a minimum 366-meter offset from neighboring lands to reduce predator access, size restrictions to limit resources available to predators, and elevation limitations to promote tidal exchange and natural wetland development. Wetland and bird island placement areas used during routine maintenance dredging are environmentally preferred and are cost effective. Using existing landforms as containment and allowing free-flowing dredged slurry to create broad tidal flats eliminate the need for dikes. A navigation channel in the bayou supports over 4,000 vessel trips annually and is the only alternative to the GIWW when the Inner Harbor Navigation Canal Lock is out of service.

Using Natural Processes

The National Audubon Society has identified the bird nesting islands as an Important Bird Area because of the essential habitat they provide to significant numbers of breeding Caspian (Hydroprogne caspia) and gull-billed terns (Gelochelidon nilotica), brown pelicans (Pelecanus occidentalis), black skimmers (Rynchops niger), and other colonial nesting seabirds. The islands’ success as nesting habitat is due to a combination of factors: their remote location discourages terrestrial predators, their small size limits the spread of avian diseases, the presence of bare sand promotes nesting by certain bird species, and the islands’ elevation is sufficient to prevent tidal and storm-driven inundation.

Gunn Island in May 2021 soon after sediment placement and before breeding by coastal birds had begun.

(Photo by Michael Guilfoyle)

Broadening Benefits

In 2020, Gunn Island, one of the Baptiste Collette Bayou bird islands, hosted Louisiana’s most significant nesting tern colony, which was believed to have been displaced from the low-lying Breton Island by tropical storm overwash. Gunn Island was specifically designed for use by nesting seabirds; surveys of the Gunn Island seabird colony in 2021 observed over 77,000 nesting seabirds from 68 species. Almost half (45%) were royal terns (Thalasseus maximus). The remaining included 21% black skimmers, 14% sandwich terns (Thalasseus sandvicensis), 8% gull-billed terns, 5% Caspian terns, 5% laughing gulls (Leucophaeus atricilla), and 2% of 19 other species.

Coastal birds on Gunn Island in 2020. That summer, the island’s royal tern nesting colony—the largest in Louisiana—was estimated at 50,000.

(Photo by P.J. Hahn)

The black skimmer is one of the native seabird species that uses Baptiste Collette Bayou islands for nesting and other activities.

(Photo by P.J. Hahn)

Promoting Collaboration

Summer 2020 brought Louisiana’s largest colony of some 50,000 nesting royal terns to Gunn Island just as dredged material placement began for the year’s Baptiste Collette Bayou maintenance. The state and federal fish and wildlife departments helped the CEMVN survey the island’s nesting birds and establish equipment corridors to reduce disturbance from ongoing dredging activities. After completion of the 2020 maintenance cycle, U.S. Geological Survey ornithologists were contracted to regularly survey Baptiste Collette Bayou’s island and wetland habitats and develop design goals for future beneficial use activities that could make them more productive nesting, foraging, and overwintering grounds.

Tern nestlings hatched on Gunn Island. Sediment dredged from the adjacent federal navigation channel provides the habitats needed to sustain native seabird populations.

(Photo by P.J. Hahn)