The eagle has one of the most powerful eyesight in the animal kingdom, estimated to be 4 to 8 times stronger than an average human. An eagle is believed to have spotted a rabbit 2 miles (3.2 km) away. Despite only weighing about 10 pounds (4.5 kg), an eagle's eyes are comparable in size to a human's. As the eagle swoops down from the sky to attack its prey, the muscles in its eyes continuously adjust the eyeballs' curvature, allowing the bird to maintain sharp focus and accurate perception throughout the approach and attack.