 Two species of birds in the park are in danger of disappearing. The range of the Cape Sable seaside sparrow is restricted to Everglades National Park and the Big Cypress Swamp. In 1981 6,656 Cape Sable seaside sparrows were reported in park boundaries, but surveys over 10 years documented a decline to an estimated 2,624 birds by 2002. Attempts to return natural levels of water to the park have been controversial; Cape Sable seaside sparrows nest about a foot off the ground, and rising water levels may harm future populations, as well as threaten the endangered snail kite. The Everglades snail kite eats apple snails almost exclusively, and the Everglades is the only location in the United States where this bird of prey exists. There is some evidence that the population may be increasing, but loss of habitat and food sources keep the estimated number of these birds at several hundred.
