The cranes using the Platte River is not a new phenomenon. Fossil remains of a sandhill crane date as far back as 8 million years.
During the day the sandhill cranes feed on waste corn in corn fields adjacent to the Platte River. The corn is about 90% of their diet. The remainder of their diet consists of insects, earthworms, snails and plants. During their stop in Nebraska, cranes will gain nearly 10% of their body weight.
The cranes spend the night on sandbars in the Platte River. The river offers the cranes protection from predators during the night. Being in a blind along the Platte River to watch the cranes come back to the Platte at night, or to watch them lift off in the morning is an awesome experience. I did neither this year. But watching them feeding in the corn fields is interesting also.
More about Sandhill Cranes can be found here
UPDATE: Sunday morning March 22.
The Lincoln Journal Star has an article about the sandhill cranes in todays paper.