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Sites used on the Platte River over the past two decades conform with these criteria. Usually, Platte River stopover sites are at least 0.25 -mile from bridges, roads, and occupied dwellings. Upstream and downstream visibility at Platte River roost sites averaged 1.2 miles (Faanes 1992). Analysis of 62 confirmed use sites on the Platte River indicates a strong whooping crane selection of the widest available channels (i.e., channel width is the distance across the active channel bed, where horizontal view is unobstructed by perennial, woody vegetation or channel banks) (FWS, unpublished data). Use of channels wider than 900 feet is disproportionately high in relation to their low availability. Channels less than about 500 to 700 feet wide appear to be selected against, and channels less than 500 feet are seldom used. The sites used for roosting were typically filled with water or nearly so. The total wetted width was generally 90 to 100 percent of channel width (median 94 percent, range 55 -100 percent). The water depths vary across the channel at each site, providing shallowly submerged sandbars and deeper channels around the sandbars (Faanes et al. 1992). The deepest channel at the sites has ranged from 1.5 to 3.5 feet (FWS, unpublished data). Using habitat characteristics of known whooping crane use sites, the Biology Work Group of the Platte River Management Joint Study (Joint Study) modeled roost habitat quality on the Platte as a function of river discharge. This application was undertaken by the FWS, BOR, and many participating federal, state, and private agencies during 1984-199' ) as part of the Joint Study of endangered species (BOR 1987; FWS 1987b). Specialized adaptations of the Instream Flow Incremental Methodology (IFIM) (Bovee 1982) were used. Habitat criteria applied in the Biology Work Group model were lack of disturbance, channel width, width of water in the channel, and a function that evaluates a range of water depths (both shallowly submerged sandbars with deeper water). Whooping crane authorities agree that whooping cranes select roosting sites on the basis of the security offered by the site(s) (Shenk and Armbruster 1986; FWS 1987b). The security value of whooping crane riverine roost sites is a function of the following habitat model criteria: 1. Unobstructed channel width: Whooping cranes require roosting sites free of visual obstructions, or an unobstructed view, presumably to allow them to see approaching predators. An unobstructed channel provides `escape' cover, and is necessary to allow an expanse of water, discussed below. 2. Presence of water: Whooping cranes roost standing in water. The availability of water is an inherent requirement in sandhill and whooping crane behavior. 3. Depth of water: Recent sightings indicate whooping cranes use shallow submerged areas bounded by deeper water. On the Platte River, water conditions provide shallowly submerged sandbars bounded by deeper water in main channels (FWS 1987b, 1993; Faanes et al. 1992). 4. Water width: In addition to simply being present and having adequate depths, the expanse of water surrounding the roost must be sufficiently wide to provide a sense of