Overpopulation occurs when more Eagles hatch than can survive. Not all of the Baby Eagels survive due to other animals eating them
There are variations if eagles- some are bigger and some are smaller. The bigger variation is selected for in favor of natural selection
#5 Adaptation and selection
Eagles have preditors, but preditors only feed on the young, one of the eagle's preditors are (owls) which come at night when the eagles cant see and swoop to eat the young eagles
# Differentail reproduction
Eagles compete for food with other eagles, they also compete for sticks and other things to build nest and spaces to build the nest. They also have to worry about keeping as much young to survive as possible.
Bigger is more selected than smaller eagles. Bigger eagles have adapted to picking up bigger fish and rodents. While smaller eagles are stuck having to find smaller fish rodents which are a little harder to find..
Throughout years of Evolution, natural selection, and speciation there are different types of eagles, bigger eagles like Blad eagles tend to nest near rivers where big fish are, and smaller eagles tend to nest near fields where smaller rodents wonder