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Each spring about 80%of the sandhill cranes in North America stop for several weeks in the Platte and North Platte River Valleys of Nebraska while en route to breeding grounds in Canada, Alaska, and the Soviet Union. This concentration of cranes is unparalleled in North America and these sites represent the principal spring staging areas for the midcontinent population. Large numbers of waterfowl, numerous bald eagles, whooping cranes, and many other species also use the area.
Recent changes in habitat conditions along the Platte and North Platte Rivers have prompted concern for the welfare of sandhill cranes and other migratory birds found there. With approximately 70% of the Platte's annual flows diverted for various consumptive uses upstream in Colorado, Wyoming,and western Nebraska, channel width in many areas has been reduced to 10-20% of former size. Habitat conditions within the existing channel have also changed as a result of reduced scouring of sandbars and shifting of alluvial sediments. A broad band of mature deciduous woodland now occupies tens of thousands of acres that formerly were part of the river and numerous islands overgrown with woody vegetation exist within the channel. Concurrent with diminishing surface flows in the channel, tile water table beneath adjacent native grasslands has declined, thereby facilitating extensive conversion of these sites to cropland.
In 1978, the U.S. Fish and Wildlife Service began a 3-year investigation to define habitat-use patterns and habitat requirements of migratory bird populations utilizing the North Platte and Platte River Valleys in Nebraska and to assess factors influencing woody vegetation establishment along these Rivers. Concurrent investigations were conducted by the U.S. Geological Survey and the U.S. Water and Power Resources Service to identify flows necessary to maintain desired levels of migratory bird habitat and locate potential sources of water to be utilized in habitat maintenance.
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