@Joe Nation,
four eggs, if gone to term, will produce possible only one sibling that survives. Two or three will not be fed properly and will either starve or be killed by the siblings.
Its sad but theyve learned that, with eagles, anything over 2 eggs usually have that turnout (peregrines are worse because they tear chunks of meat to feed the chicks) while eagles , after the first few days, just DUMP a fish into the nest an the chicks tear it apart.
In the old days, "hacking" was the term for stealing one of three eggs from a nest and incubating it and rearing the chick to be transplanted into areas where the eagle populations had crashed.