The birds take turns being in the front, falling back when they get tired. In this way, the geese can fly for a long time before they must stop for rest. The authors of a 2001 Nature article stated that pelicans that fly alone beat their wings more frequently and have higher heart rates than those that fly in formation. read more
In fact it is not only cranes but most migrating birds fly in a V formation. A study of ibises birds was done to find any potential clues. The finding was that these big-winged birds carefully position their wingtips and sync their flapping, presumably to catch the preceding bird's updrift and save energy during flight. read more
If you are #2 in a 2-plane formation, it is far easier than being #4 in a 4-plane formation. Movement down through the formation flight of four becomes more difficult and exaggerated with each successive aircraft. As #4 if flying in echelon you will be feeling the effects of being at the wild end, “crack the whip” style. read more