Congress established the Snake River Birds of Prey National Conservation Area (NCA) in 1993 to protect North America's, and possibly the world's, largest concentration of birds of prey. They include bald and golden eagles, several species of owls, peregrine falcons, prairie falcons, kestrel, merlin, and others. The NCA covers 485,000 acres along 81 miles of the river canyon. In addition to nesting habitat along canyon walls that tower up to 600 feet high, this area includes 420,000 acres of critical prey habitat."It is not possible to go in any direction from this area without losing several of the important characteristics that make up this remarkable situation. The soils change, the geology changes, the climate changes; and in no other area in the Northern Hemisphere do these combinations of factors occur to such benefit to the birds of prey."
- Raptor expert Morley Nelson, quoted on BLM website
About 14,000 years ago, as glaciers receded from the last ice age, the 20,000 square mile Lake Bonneville crested at Red Rock Pass, Idaho, creating what is known as the Bonneville Flood. As soft soils eroded at the pass, the lake poured into the volcanic plain of the Snake River and its canyons. Today, visitors to the Snake River area can explore the house-size boulders, box canyons, and other evidence left behind by the tremendous flood. At Swan Falls, peak discharge of the flood was an astounding 33 million cubic feet/second.
In the Snake River ecosystem, a unique combination of climate geology, soils, and vegetation supports extraordinary numbers of predators and prey. More than 700 pairs of raptors, representing 15 different species, nest on the high canyon walls. Nine additional raptor species use the Snake River area as seasonal hunting grounds during migrations or as wintering areas. Birds of Prey NCA is particularly important for prairie falcons, North America's only indigenous falcon. The area is home to a significant portion of the species' known population.
Unusually high numbers of small burrowing mammals, which make their home on a plateau rich in vegetative cover and ideal soil, support a high density of raptors. Paiute ground squirrels, the main prey of the prairie falcon, are the most abundant of the burrowing creatures (in fact, according to the BLM, portions of the Birds of Prey NCA support the densest ground squirrel populations ever recorded). Nesting success for prairie falcons is linked very closely to the squirrel abundance. Similarly, the success of golden eagles and other raptors is tied to the great quantity of black-tailed jackrabbits. Additionally, abundant prey and deep soil support one of the densest populations of badgers in the world (up to 11 badgers per square mile).
Unfortunately, recurring wildfires and military training exercises at Snake River have dramatically altered the prey base for the raptor population that the NCA was established to protect. As a result, the raptor population is at currently risk. A Bureau of Land Management (BLM) study documents that nesting prairie falcons in the NCA have declined from a historical 230 pairs to an estimated 110 pairs today.
In addition to its precious natural resources, Snake River Birds of Prey NCA has significant cultural value. Human occupation of the Snake River area has been dated to 10,000 BC. Shortly after the Bonneville Flood deposited large rounded boulders in the canyon, early inhabitants were using them as canvases for carving petroglyphs. Some of the oldest and most remarkable Native American Archeological sites in Idaho have been found within the NCA. The NCA also contains some of the best-preserved portions of the Oregon National Historic Trail and three sites from an 1860's gold mining settlement that are listed on the National Register of Historic Places.
Congress designated the NCA on August 4, 1993, following two decades of research indicating the need to protect prey habitat and hunting territory as well as nesting habitat. The expressed purpose of the NCA, according to Congress, is "to provide for the conservation, protection, and enhancement of raptor populations and habitats...." Currently, the BLM allows ranching, power generation and Army National Guard training to continue within the boundaries of the NCA.