The sandhill crane is the oldest living species of bird, with fossils dating back six million years. Many biologists believe the sandhill has been virtually unchanged for nine million years. Their gray plumage is offset only by a bare red crown, white cheek feathers, and a black bill, legs and feet. Males are slightly larger than females, but the sexes look alike and can best be distinguished by their behavior during mating displays. Young birds look similar to adults, but have gray feathers in place of the red skin on their crowns.
Cranes are a very secretive species requiring large, open freshwater wetlands and shallow marshes.
Otter Creek Marsh fits the habitat needs of the sandhill crane. Otter Creek Marsh comprises some 3,500 acres on the floodplain of Otter Creek and the Iowa river near Chelsea in southeast Tama County. The marsh consists of eight individually managed segments. The refuge provides protection for the many thousands of waterfowl that migrate through this area in the fall. The best time to see the sandhill cranes is in the morning or early evening.