Because they have different Cones. Which simply means that some animals see certain types of colors or even Infrared or Ultraviolet, in which Humans cannot see.
The bald eagle and the black bear are tetrapods, which means that they both have four limbs along with the digits. This shows that they both are the descendants of the four-limbed ancestors. However, the limbs of the bear and the bald eagle have different functions. The forelimbs of both these organisms serves different purpose. Hence, their limbs are homologous organs. The homologous organs are those which have the same ancestry but the functions are different.
