Harpy Eagle with Neil Rettig. The most powerful bird of prey on Earth, the harpy eagle, weighs up to 20 pounds (nine kilograms), has a seven-foot (2.1-meter) wing span, and is armed with talons as big as grizzly bear claws. Those deadly talons can exert several hundred pounds (over 50 kilograms) of pressure, crushing the bones of the sloths, monkeys, and other prey the eagle snatches from the rain forest canopy, often killing its victims instantly. The fearsome predator once ranged from southeast Mexico to Argentina. Now, Panama's pristine rain forests are among the few places where the bird has survived.