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Habitat Type During a 2-month period, primarily March through April, the cranes utilize three general habitat types within this river reach (Fish and Wi 1 dl ife Servi ce, 1976): (1) shallow, submerged, unvegetated sandbars in broad stretches of ri vel', (2) wet meadows, parti cul a 1'1 y those near roosting areas, and (3) corn and milo stubble and alfalfa fields as primary feeding sites. Afforded protection from predators, the cranes use the shallow sandbars almost exclusively for night roosting. Their preferred roosting habitat is water less than 6 inches deep, a broad channel, and infrequent vegetation on the sandbars and islands (Frith, 1974). During th~-morning hours, cranes leave their watery roosts for the wet meadows. The Fish and Wildlife Service has provided this description of wet meadows: "lowland areas which are relatively free of sizeable trees and where the soil is usually without standing water during most of the growing season, but is periodically waterlogged within a few inches of the surface in scattered spots due primarily to a 'high water table. These areas are frequently undulatIng; therefore; are often basically habitat complexes. Vegetation commonly occurring may include grasses (excl udi ng feed grains ,gra ins, and/or sorghum crops), and/or ' sedges, and/or rushes, and/or small nonagricultural broadleaf plants., This wet meadow classification includes ephemeral (lasting only a short time) areas which are a gradatton between the lowest areas and the more upl and areas." Wet meadows are the cranes' "marsha ling areas," where they often group before moving ,into 'the grain fields to feed. Generally, less than a mile from the river roosts, wet meadows are used for preening, dancing, resting, feeding, and as secondary roosts. Migratory Habits The "stem of the hourglass" between O)l8r1:,on and Chapman, Nebraska, provides some of the most important habitat within the sandhill cranes' top and bottom-heavy migratory route (Fish and Wildlife Service, 1976). There is no habitat of similar quality and quantity within the, United States' portion of the Central Flyway in North America (FiSh and Witdlife Service, 1976). It is here, after a nonstop 600-mile migration from wintering areas, that the cranes choose to pause 'and replenish their energy reserves. The birds arrive at the Platte in relatively poor physical condition. Each bird stays on the Platte River for approximately 6 weeks feeding on sprouting vegetation and invertebrates in the wet meadows and waste grain and sprouts in the croplands. Each one of these types of foods provides essential elements in their diet (Fish and Wildlife Service, 1976). During this stint, each crane gains 26 _:;,-