Slow start

Yellow-eyed penguins lay 2 eggs about 3 days apart but the chicks on the same day generally because the parents don't incubate the first egg properly until the second one has arrived. They sit on them in a half-crouch to guard them. Once they have the second egg, incubation can start in earnest and way they go. The chicks hatch on the same day and are therefore the same size and one does not outcompete the other because it is a few days earlier out of the egg.