in Virginia. Water birds include sandpipers, wood ducks, and Virginia rail, while common inland examples include warblers, woodpeckers, and cardinals, the state bird. Birds of prey include osprey, broad-winged hawks, and barred owls. There are no species of bird endemic to the Commonwealth. Audubon recognizes 21 Important Bird Areas in the state. Peregrine falcons, whose numbers dramatically declined due to DDT pesticide poisoning in the middle of the 20th century, are the focus of conservation efforts in the state and a reintroduction program in Shenandoah National Park. Virginia has 226 species of freshwater fish from 25 families; the state's diverse array of fish species is attributable to its varied and humid climate, topography, interconnected river system, and lack of Pleistocene glaciers. The state's lakes and rivers are home to Eastern blacknose dace and sculpin on the Appalachian Plateau; smallmouth bass and redhorse sucker in the Ridge-and-Valley region; brook trout, the state fish, and Kanawha darter in the Blue Ridge; stripeback darter and Roanoke bass in the Piedmont; and swampfish, bluespotted sunfish, and pirate perch in the Tidewater. The Chesapeake Bay is host to clams, oysters, and 350 species of saltwater and estuarine fish, including the bay's most abundant finfish, the Bay anchovy, as well as the invasive blue catfish. An estimated 405 million Chesapeake blue crabs live in the bay . There are 34 native species of crayfish, like the Big Sandy, which often inhabit rocky bottomed streambeds. Amphibians found in Virginia include the Cumberland Plateau salamander and Eastern hellbender, while the northern watersnake is the most common of the 32 snake species. Protected lands , roughly 16.2% of land in the Commonwealth is protected by federal, state, and local governments and non-profits. Federal lands account for the majority, with thirty National Park Service units in the state, such as Great Falls Park and the Appalachian Trail, and one national park, Shenandoah. Shenandoah was established in 1935 and encompasses the scenic Skyline Drive. Almost forty percent of the park's total area has been designated as wilderness under the National Wilderness Preservation System. The U.S. Forest Service administers the George Washington and Jefferson National Forests, which cover more than within Virginia's mountains, and continue into West Virginia and Kentucky. The Great Dismal Swamp National Wildlife Refuge also extends into North Carolina, as does the Back Bay National Wildlife Refuge, which marks the beginning of the Outer Banks. State agencies control about