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\ -\ II/I\ll" , \ , ~,7J ~\..; ", ')-'{ be an espec ially important haven during years when spring arrives late. The birds may leave Aransas at the usual tnne, fly part of the way to Wood Buffalo, and then find themselves unable to proceed farther. Under such conditions it is thought that the birds may spend up to 6 weeks along the Platte. Nonethe- less, whoopers have been observed stopping at points along the Central Flyway: in Oklahoma, Kansas, Nebraska, the Dakotas, Montana, and Saskatchewan (critical habitat designations have also been made in some of the other states). Within Nebraska, whoopers have been observed using other rivers including the Repub- lican, the Big Blue, the Loup, and the Niobrara. In short, there are alterna- tives to the Platte; what is not known is whether these are sufficiently avail- able under all climate conditions, and the rate at which they are disappearing under development pressure. The support document prepared by the Fish and Wildlife Service for the proposed critical habitat designation c1anned that "Nebraska has more recorded whooper sightings than the remainder of the states combined. A recent compu- tation of confirmed sigh tings in Nebraska revealed that 77 percent of these recorded between 1922 and 1975 were on the Platte River," (Fish and Wildlife Service, 1977). These assumptions would certainly appear to establish the preeminent im- portance of the Platte River to the whoopers during migration. However, doc- umentation for these clanns was not given, and other sources do not support them. The statement about the frequency of sightings in Nebraska presumably counts only the states in the Central Flyway, otherwise Texas, their winter home, would surely predominate. Even without Texas, Nebraska in no way "has more recorded whooper sightings than the remainder of the states combined." Table IUa gives the confirmed sightings of whoopers in the Central Flyway between ~~ and 1976. Only 17% of the sightings occurred in Nebraska, less than in either North Dakota or Kansas. Furthermore, only 57% of the confirmed sightings in Nebraska between 1942 and 1976 were along the Platte (Table IIIb) of which approxnnately two-thirds were in the critical habitat area (although well over half the spring sitings were in the critical habitat). There are, of course, problems in drawing inferences from these data. For one thing, there are casual observations that may reflect the density of observers as much as the density of cranes. Besides, these data are for con- firmed sightings only. Because of the huge number (up to 200 000) of sandhill cranes that regularly stop over along the Platte each spring, sightings are {y'}-~].' 40