The 610 acres of Belt Woods contain one of the last remnants of old-growth coastal plain forest in the Mid-Atlantic region and support a forest bird community of characteristically high breeding density. Its old-growth characteristics include not only 200-year old trees of over 140 feet (45m) in height, but also unusually high densities of Forest Interior Dwelling Species of birds (FIDS).
Belt Woods is recognized as an IBA because of the unusually high population densities of Forest Interior Dwelling Species (FIDS). The Breeding Bird Census, which uses a territory mapping method, measured a density of >200 pairs/100acres (40 ha) of FIDS in 1989, attributable largely to high densities of Wood Thrush (Audubon WatchList, Yellow category) and Red-eyed Vireo. When the tract was first surveyed in 1947 the density of FIDS was 300 pairs/100 acres. Nine other species of FIDS regularly breed, including an Audubon WatchList species (Yellow category) Kentucky Warbler.
Belt Woods is a small fragment of forest surrounded by an increasingly developed landscape less than 10 miles from Washington DC. The State of Maryland bought the South Woods in the 1980s to protect the old-growth character of this 43-acre tract after the oaks of a similar tract (North Woods) were cut. The remaining 550 acres of the North and Central Woods were acquired in the 1990?s to buffer the old growth forest and prevent development. Access is limited to scientific study.