The Isles Dernieres-Timbalier Islands Important Bird Area (IBA) consists of the Isles Dernieres and Timbalier Island chains, barrier islands in the Gulf of Mexico and the offshore waters that surround them. Part of the Isles Dernieres chain is the Terrebonne Barrier Islands Refuge, which encompasses three islands, Wine, Whiskey, and Raccoon Island. The Timbalier Island chain consists of the Timbalier and East Timbalier Islands. Both of the island chains are located south of the shoreline of Terrebonne Parish. This IBA lies south of the Barataria Terrebonne IBA, which consists of many of the marshes of the southern Deltaic Plain.
The IBA?s remote location and diverse habitats make it invaluable to birds. Ranging from beaches to shrublands and coastal dunes to marshes, the barrier islands offer habitat to nesting, wintering, and migrant birds. Important birds supported by this IBA include Reddish Egret, Wilson?s, Piping and Snowy Plover, and Brown Pelican. Unfortunately, this IBA is extremely vulnerable to hurricanes, and coastal erosion and sea level rise threaten the continued existence of this IBA.
Because of their remote locations, the islands within this IBA are tremendously important for nesting, wintering, and migrant birds as they are rarely burdened with human disturbance or large populations of mammalian predators. Raccoon Island is particularly valuable for colonial nesting water birds; in fact, the island is one of the most important nesting sites for Brown Pelican in the state. Other nesting birds include Wilson?s Plover, Royal and Sandwich Tern, Great, Snowy, and Reddish Egret, and Great Blue and Tricolored Heron. In addition to nesting birds, these islands are also possibly the most important wintering sites for Piping Plover and Snowy Plover in Louisiana. Sanderlings also winter here. Long-billed Curlew, Red Knot, and a variety of shorebirds use the site for wintering or stopover migration. This IBA sometimes functions as an emergency stopover site for migrating landbirds such as various warblers, tanagers, grosbeaks, and cuckoos.
This site?s primary threats are coastal erosion and sea level rise. The increasing frequency and severity of hurricanes threatens the actual existence of the islands. Other threats include offshore oil spills. Mammalian predators that do rarely make it to these islands can have a severe impact, particularly on nesting birds. Human disturbance, while very rare, can occur if people trespass on the islands.
The Terrebonne Barrier Island Refuge, again consisting of Wine, Whiskey, and Raccoon Islands, was acquired in June of 1992 from Louisiana Land and Exploration Company via a 25-year free lease. The refuge is currently managed by Louisiana Department of Wildlife and Fisheries. Other islands including Timbalier and East Timbalier, are privately owned.
The islands within the IBA offer a variety of habitats for the birds utilizing the site. The Gulf sides of the islands are covered with sandy beaches that grade into coastal dunes and then to grasslands. Plants found in the grasslands include sea oats and beach morning glory. Shrublands follow, with their vegetation a mix of baccharis and wax myrtle. On the back edges of the islands is a combination of salt marshes and mangroves containing plants such as Spartina alterniflora, widgeon grass, and black mangroves. Many of these islands have been adversely affected by hurricanes; as a result, restoration efforts to close breeches in the islands, nourish the beaches, and create marshes have been combined with vegetative plantings in an attempt to help secure the dredged material. Wine Island recently received a rock perimeter to restore habitat damaged by hurricanes.
This IBA is used primarily for research purposes, most recently by Louisiana State University (LSU), Nicholls State University, and University of Louisiana, Lafayette (ULL). The islands of the Terrebonne Barrier Island Refuge are closed to the public although adjacent waters may be used for a number of purposes including recreational fishing and swimming and commercial fishing and shrimping. The other islands are open to the public, though they are not very accessible, and thus have low impact from human use. There is some oil and gas exploration. There are many ongoing restoration efforts such as inflation of breakwater structures and pumping sand to build up the islands? elevation. These restoration activities are headed up by a combination of state and federal groups, including the U.S. Army Corps of Engineers, National Marine Fisheries Service, and the Louisiana Department of Wildlife and Fisheries.