Organizing for Endangered and Threatened Species Habitat

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1. shallow water-preferably on submerged sandbars surrounded by deeper water. These areas must be surrounded by wide open spaces around the roost- a radius of at least 250 yards; 2. sandhills put on fat-20 to 25 % of their body weight must be put on while on the Platte, both for the journey north and for surviving early days after arrival in the arctic when food is still scarce; whoopers tend not to stay in the central Platte sufficiently long to put on such high proportions of fat; they need wet meadow complexes adjacent to the Platte-these serve as a source of protein and minerals needed to trigger breeding processes. Much of the traditional wet meadow area upon which both species of cranes depend has been lost to irrigation and river channelization. Yet, by early March in a typical yea.r almost one half million sandhill cranes will be packed into 60 miles of river along the central Platte, taking refuge on sandbars in shallow water. A major impact of upstream water capture and use has been a reduction of channel width and channel area (Figure 4). According to land survey maps, channel widths in 1965 were 21 to 73 percent of the 1865 widths recorded. 1938 ,., . ??,,,,_..r.?,. ;,•Y::?''?? ?- `? ;G`r -'a,,.r,m.-. Ftv? ??k;?'+n,?sl-?,?i? •'r'????...._ti`•??-?"+??„*?,s.a?,?rt'^CLr:rp 1469 \,?.?..?:.r.k:?-'-L•:.. . ,_••,?.?- ?.o$S?jtKi"G.?1..r.i??w'.'+`..°?`?"'?W'_°-? „?„a,,,,?.<.,wm•:•a'? ............? ?? ; .?r-.?y.?•?''?--'. •,°??-s?v°'?? ..?: ...? ??. :-? '. .... . ... ...? 41 1982 _--? 0 .2b .5 1 Source: Currier at ai, 1985 Mpes Figure 4 Increased Channelization of the Platte Because of controlled releases from reservoirs upstream, there is less variability in over-all river flows than there were historically. The Pathfinder Reservoir, completed in 1909, was the first major impoundment on the North Platte, followed by Guernsey (completed in 1927), Alcova (1938), Seminoe (1939), McConaughy (1941) and Glendo (1957). These reservoirs dropped annual average peak flows on the North Platte by 86% (Currier, Lingle, and Walker 1985: 96). This change has resulted in a net loss of water-filled channel and an associated increase in vegetated river- banks. This, in turn, has meant loss of roosting, nesting and feeding habitat that comes with loss of ineanders and grasslands- wetlands near the main river channel. Reduction of available habitat for all the species of birds that traditionally made use of the Platte basin creates two forms of hardship: 1) competition for the limited food supply; and 2) crowded conditions exacerbates disease transmission. Avian cholera and 12