Also, in a big group the small cranes could get lost. It would be easier to keep track of smaller groups than in one huge group. 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 inexperence 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. They can also have smaller nesting areas to hide from thier enemies. It might be easier for a small group to find a place to rest. All Rights Reserved.