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physiologically and nutritionally for the main portion of their southward <br />migration. Accordingly, the species use of habitat in this geographical area <br />is especially deserving of further study and management focus. <br />Habitat Use Along the Migration Route (Section 2.7): Whooping cranes are <br />annivorous feeders and seem to easily adjust to whatever suitable plant and <br />animal foods they encounter at migration stopover locations. Al ong the Platte <br />River, as well as elsewhere along the flyway, grain fields appear to be used <br />prominently as feeding sites indicating the species' successful adaptation to <br />cultivated crops (e. g. , barley, wheat, corn, mil o, and sorghum) which are <br />readily available throughout the migration corridor. Feeding in wetlands <br />typically consists of foraging in the vicinity of roosts. <br />Migrant whooping cranes are flexible in their selection of stopover sites along <br />the flyway and utilize a wide variety of natural and man-developed or modified <br />habitats within the prairie-plains region of the central United States and <br />southcentral Canada. Major prerequisites of suitable stopover locations appear <br />to be the presence of shallow water (standing or flowing) for roosting, good <br />horizontal and overhead visibility, close proximity to feeding sites, and <br />reasonable isolation from human developments and /or disturbances. <br />Recent monitoring of radio-tagged whooping cranes has, for the first time, <br />permitted the systematic documentation of each stopover site used by individual <br />birds (and their traveling companions) during a complete migration. The <br />pattern emerging from available data is that small wetlands, both natural and <br />manmade, are generally selected as roost sites; e. g. , small boreal lakes, <br />"pothole" ponds, farm ponds and stockponds of 5 acres or less, and flooded <br />grain fields containing as little as 1/4 -acre of open water (approximately 105 <br />X 105 feet of surf ace area) . These findings i ndi cate that migrant whooping <br />cranes will readily stop at wetlands containing only a limited amount of open <br />water if the site offers the necessary visibility, security, and access to food <br />that the birds require. <br />Based on radio-tracking observations, the tendency of migrant whooping cranes <br />to select small wetlands as stopover roosts is apparent in Nebraska as well as <br />elsewhere along the U.S. portion of the flyway. Among the 27 migratory fl ight <br />passes by individual birds (including juvenile, subadul ts, and adults) <br />monitored through the state of Nebraska during the nine radio-tracking efforts <br />f ran 1981 -1984, no stopovers were observed along the Platte River. Duri ng <br />three tracking efforts (one in the spring involving three birds, and two in the <br />fall involving a total of five birds),-no stopovers occurred in the state. <br />Though whooping cranes are dependent on traditional ( fixed) nesting and <br />wintering grounds, radio-tracking studies have provided empirical proof that <br />migrant birds are not dependent on specific stopover sites along the flyway. <br />Rather, whooping cranes exhibit a nontraditional (opportunistic) habitat <br />selection strategy along the flyway which is of direct survival advantage in <br />that it allows freedom of response to the various hazards and rigors of <br />migration (e.g., severe weather, fatigue, and hunger). Moreover, this strategy <br />enables the species to adjust to changing habitat conditions within the migra- <br />tion corridor as influenced by natural and human factors (e.g., climate-induced <br />iii <br />