I bet today is the day they leave. I wish I was out there watching them pick up that last bite of blue crab for their journey. They were blown out of the usual mid-Nebraska migration corridor by a strong storm that later caused devastating tornados in Ohio. Present were six cranes near DeSoto NWR, and a family group near Essex in Page County. If they were all in one big group they would have to find food for all the birds instead of just five or six.
Smaller groups can fly at different rates to help the inexperienced flyers.
Other groups can move at a faster rate. When they travel in small groups they can hide easier instead of being spotted by a predator which might kill some of the cranes. And it might be easier for a small group to find a place to rest. Also the way feathers are shaped that if a bird was to turn around the feathers would ruffle and may be damaged. If they were to turn around their tail feathers might make the bird flip over and over and it might break its bones.