Somerset-Wicomico Marshes IBA extends along the Chesapeake Bay shore from near the Virginia line at Pocomoke Sound north to the town of Nanticoke, and includes all saltmarsh within Somerset and Wicomico Counties. These marshes, along with the vast marshes of neighboring Southern Dorchester County IBA, constitute one of the largest complexes of saltmarsh on the Atlantic coast of North America. Also included are several areas of loblolly pine forest adjacent to the marshes and within the same Green Infrastructure hubs. The site encompasses the lower reaches of three rivers, the Annemesses, Manokin and Wicomico. Much of this site is privately owned, including Irish Grove Sanctuary, which is owned and managed for birds by the Maryland Ornithological Society. Protected areas of public land owned by Maryland DNR include Ellis Bay WMA, Deal Island WMA, Fairmount WMA, Cedar Island WMA, Pocomoke Sound WMA and Jane Island State Park. The Monie Bay section of the Chesapeake Bay National Estuarine Research Reserve is owned by the federal National Oceanic and Atmospheric Administration (NOAA) and is jointly managed by NOAA and Maryland DNR.
This large expanse of primarily tidal marsh regularly supports virtually the full complement of breeding bird species to be expected in saltmarsh and freshwater marsh in Maryland. Breeding birds include four Audubon/American Bird Conservancy WatchList species (Red category: Black Rail, Saltmarsh Sharp-tailed Sparrow, Seaside Sparrow; Yellow category: King Rail), and two species listed by Maryland DNR as In Need of Conservation (American Bittern, Common Moorhen). Black Rail was listed as Endangered by the State of Maryland in 2007 due to a rapidly declining population. Another WatchList species in the Yellow category, Short-eared Owl, winters in significant numbers. The upper edges of the tidal marshes may be important for the rapidly declining Northern Bobwhite, and are likely to assume greater importance for this species as agricultural lands become increasingly efficient. Deal Island WMA is one of only two breeding locations in the state of the Black-necked Stilt, which began nesting here in the 1980s. A 2,800-acre impoundment at Deal island WMA attracts >200 wading birds in Fall, including sizeable flocks of Black-crowned Night Heron, Tricolored Heron, and Glossy Ibis.
Like most tidal marshes in the region, introduced species pose a large threat to this site. Nutria, introduced from South America as a furbearer, destroy marsh plants by eating them. This leads to erosion of the marsh habitat. Phragmites, an introduced reed, invades the upper reaches of the marsh, where it reduces the habitat value of habitat by altering the vegetation structure. Sea level rise presents a long-term threat.