Emperor penguin chick
As soon as the egg is laid (penguins lay one or two eggs at a time), the female dashes out for dinner, leaving the male to watch the nest.
When the female returns (it can take up to two weeks for her to come back) it's the male's turn to head out for food, leaving the female with the egg.
When the chick hatches, it immediately starts calling so that its parents will learn to recognize its voice
Once the chick is strong enough, both parents head for the ocean at the same time. The chicks are left in a group together (sort of like a daycare). When the penguin parents return with dinner they recognize their chick by its voice.