1. Pick a crane with beautiful plumage.
Every crane want to be sure a potential mate has really healthy plumage. It shows they’ve had a good diet. The better nutrition they’ve had, the better they’ve been at getting nutrition—and thus the better they'll be at getting nutrition to their chicks. Good plumage also shows they have not been sick, but concentrated on keeping well groomed. After all, cranes that aren't able to keep themselves perfectly fit aren’t going to have the time to raise chicks.
2. Pick a crane that's strong and aggressive.
If more than one crane is competing for a bird of the opposite sex, they want the one that fights the hardest for them. That means showing aggression and strength, but also gentleness to the potential mate. A strong and aggressive bird will be able to defend their territory and keep the babies protected and fed.
Who Picks Whom?
Does the male pick, or does the female pick? It partly depends on which gender has more members. The choice is tricky for both males and females in a species like Whooping cranes, where there aren’t a lot of choices because the population is small. Dancing together indicates that it’s a really serious choice for both of them.