They reproduce a surplus of babies that makes too much for the ecosystem
adaption
And because the parents were red and brown they reproduced babies both red and brown
the end
The eagle sees and abundance of food and sees red snakes and brown. Because red seems to be a dangerous color, the eagle goes for the brown snakes instead
Now the population is died down and there are more red snakes then brown
Now the red snake will produce more and the population will have more red then brown snakes