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Located just offshore Mt. Pleasant in Charleston Harbor, Crab Bank is what is known as a Sandpit Island formed by sediment deposits from nearby Shem Creek. Though charts show that a large sand bar existed in this location for at least 250 years, Crab Bank finally became an island in the late fifties as a result of dredge spoils from Shem Creek. Though the island itself has never sunk back beneath the surface, it is constantly expanding and contracting, changing shape and size (see images below).
With 22 acres, Crab Bank provides a variety of habitat that allows it to support wildlife, including intertidal beach, mudflats, and maritime grasslands. Due to its isolation, sufficient height to prevent over-washing, and lack of predators in the forms of rats and raccoons, the island provides an ideal habitat for a seabird colony, for which all of these factors are a must. In fact, Crab Bank is one of only nine active seabird nesting sites in the state and hosts a large percentage of South Carolina’s nesting seabirds each year.
The first documented seabird nesting on Crab Bank took place in 1979, likely the year in which it gained sufficient height to prevent over-washing, and since then has become one of the most important breeding sites for seabirds in South Carolina. Fifteen species of birds have been known to breed on the island, with some numbering in the thousands. Of these, one is State Threatened, two are State Species of Concern, and one was formerly considered Federally Endangered. However, nearly all of the species are considered to be in decline, and Crab Bank offers them crucial habitat. The nature of their nesting makes all of these species highly vulnerable, with single events such as hurricanes or a loose dog severely damaging a colony. With so few colonies along the South Carolina Coast, maintaining these nesting sites can mean supporting a large percentage of the statewide population. This is certainly the case with Black Skimmers, with up to 68% of the total South Carolina population nesting on Crab Bank depending on the year.
A variety of species use Crab Bank for breeding during the summer months. During the breeding season, one can find Brown Pelican, Least Tern, Royal Tern, Black Skimmer, Gull-billed Tern, Sandwich Tern, Common Tern, Laughing Gull, Wilson’s Plover, American Oystercatcher, Willet, Great and Snowy Egret, Tricolored Heron, and White Ibis nesting on the island, though their numbers vary from year to year. In addition, many species use the beaches and mudflats of the island for wintering grounds throughout the rest of the year, and a trip out to Crab Bank may find Double-crested Cormorants, Ring-billed Gulls, Greater Black-backed Gulls, as well as a variety of shorebirds including Black-bellied Plovers, Semipalmated Plovers, Sanderlings, Dunlin, and Dowitchers. Some species, such as Pelicans and Royal Terns, use the island year round.
In 1986, some protection was achieved for these seabirds through the establishment of the Charleston Harbor Wildlife Sanctuary. This refuge, expanded a decade later, worked to protect wildlife in much of the harbor and surrounding areas, stating that “It is unlawful for any person to hunt, trap, molest, or to attempt to take or molest in any manner, any wild bird, bird egg, or mammal within the sanctuary.” Even after this designation, however, the birds were still often subject to disturbance from boat landings on the island during the nesting season and particularly the dogs that accompanied their owners. In 2005, though, Crab Bank, along with Deveaux Bank and Bird Key/Skimmer Flats along the coast, were designated as bird sanctuaries by the South Carolina Department of Natural Resources, lending even greater protection to the bird colonies inhabiting these islands. Now, Crab Bank is closed to landings March 15th to October 15th during the nesting season, and only open to public below the high-tide line during the remainder of the year. Dogs are always prohibited on the island, as is camping. This amazing collection of birds can be viewed in the summer from the water.
Bird populations have continued to show a positive response to this protection. From 2005 to 2006, numbers of Royal Tern nests on the island rose dramatically from 346 to 1639. For this species, preservation of nesting sites has seen considerable success, slowing their annual rate of decline from 15,000 nests per year to 5,000. Black Skimmers showed an immediate response to the greater protection as well, with 43 nests recorded in 2005 and 200 recorded in 2006. The island continues to provide crucial nesting grounds for large numbers of Brown Pelicans. With numbers of many of these species declining, Crab Bank provides a crucial breeding ground that the birds can find in few other locations on the South Carolina Coast. Considering the vulnerability of these colonial nesters, too, it is vital that this remaining refuge be protected.
Currently, one of Crab Bank’s primary threats is erosion, which has been steadily eroding the island over the recent years and reducing Crab Banks potential area for nesting. Though a natural process, it is suspected that the erosion has been intensified in recent years due to increased shipping traffic in Charleston Harbor and the wakes created by these large boats. Even with this threat, however, Crab Bank remains a vital sanctuary for these seabirds. In 2012, the island hosted 79 Black Skimmer nests as well as 463 Brown Pelican, 1581 Royal Tern, and 475 Sandwich Tern pairs.
Due to constant erosion and soil deposition, Crab Bank remains constantly in flux, changing shape dramatically from year to year. The following photos are from 1989, 2003, and 2013:
(Images from Google Earth)