Twin Capes Focus Area
This area is one of the most important migratory stopovers in the world. Due to the orientation and funnel-like shape of the two peninsulas, migratory songbirds and raptors (with a high proportion of juveniles) become concentrated along the coast and on the peninsulas during the fall migration. Migrating birds may rest and feed in this area for several days before continuing their migration. Some birds move some distance up the NJ bay coast and probably the VA/MD Eastern Shore before crossing in the bays. It appears that the coastal marsh edge is a habitat line followed by many fall-migrating birds that avoid the open water Delaware Bay crossing and seek a shorter crossing up-bay. Recent work using weather radar to identify stopover habitat preferences of song birds in this area indicates that forested wetlands seem to be preferred habitat.
Historically, the coastal plain was dominated by mostly contiguous forest. Today, these forests have become badly fragmented by 300 years of land clearing, agriculture, and human development. Forest fragmentation and loss have reduced the available habitat for forest nesting birds, particularly those dependent on interior forest conditions. These birds depend heavily on the remaining patches of forested upland communities. At least fourteen high priority species rely on forested interior habitat including the cerulean warbler.
At one time the Delmarva fox squirrel (Sciurus niger cinereus) ranged widely throughout the Delmarva Peninsula and Southeastern Pennsylvania. Currently the stronghold is the Delmarva Peninsula in the vicinity of Blackwater NWR. Small populations exist in other areas, including the Prime Hook NWR area.
Unique and important landscape features in this area are the isolated freshwater coastal plain ponds (Delmarva Bays) and associated upland forested habitats that are concentrated along the Maryland-Delaware border. Origin of these formations is unknown though meteorites, sinkholes, whales, wind, and chunks of ice from glacial outflow are a few of the theories. Their isolation results in a unique assemblage of species. Delmarva Bays support 68 percent of the amphibians of the Delmarva Peninsula and 61 rare vascular plants including the federally endangered Canby’s dropwort (Oxypolis canbyi).