How does this instinctive behavior help whoopers survive?

Wild Whooping Cranes
When two baby cranes in a nest DO survive, they can't waste time bickering, especially in years when food is scarce. The smaller one (who hatched a day or two after the bigger one) keeps out of the way. If the smaller one isn't careful, the bigger one may grab it by the back of the neck, peck at it, or chase it. But the smaller chick quickly figures out that it's a good idea to simply avoid its big sister or brother so it won't be hurt or killed.

Captive-raised Whoopers
The baby cranes that were costume-raised must deal with something that wild whooping cranes never do: a whole group of other baby cranes. There's plenty of food for all of them, but they still instinctively need to sort out who's top dog — or rather, top bird. Each crane quickly learns its place, so the whoopers don't waste precious time and energy fighting!

Read more about pecking order. >>