Woooo! Look at those yummy baby snakes! It must taste delicious!
Due to the mutation, the eagles can not see the tan snakes. The tan snake's offspring is a tan color too, which makes them blend in with the ground, and that's why the eagles can only see the red snakes.
ooh, that's juicy!
nom nom nom
Since the red snakes stand out more on the ground, which the eagles would eat more of the red snakes than the tan snakes, this leads to the red fish population will soon died out.
Ha! I got the biggest snake!
Several years later, the whole population of snake would be tan, which make the eagles even harder to find food at this area, so the eagles had to change location, and this continue like a cycle which is called the natural selection.
There's no more snake here, let's go to another place!