The eyes of eagles are very large in proportion to their heads, and their pupils are particularly big. These impressive organs allow them to see five colors rather than just our three basic colors, and their eyes have five times more light-sensitive cells in the retina. Although an eagle may only weigh about 10 pounds, its eyes are roughly the same size as those of a human. An eagle can see something the size of a rabbit more than three miles away. Given these facts, it’s unsurprising that eagles are said to have the best vision in the animal kingdom.
There is a scientific set-up to determine the acuity of an eagle’s eyesight. The birds are trained to fly down a long corridor where two screens are installed at the end. One screen has a display of striped patterns to attract the eagle towards it. The Eagles’ acuity is tested by making micro changes to the width of the stripes and determining from what distance the eagles begin to turn in the correct direction.