Laserfiche WebLink
(Allen, 1969). There is seldom a bxeak in the fierce alertness in resisting intrusion of any other <br />whooping crane pair. Most whoopers leave their northern breeding grounds by the end of <br />September but often do not arrive a.t their gulf coast wintering grounds until December. Pairs <br />with newly-fledged juveniles typically are the last to arrive. They also display much solidarity in <br />the simple family unit protecting and nurturing fledglings until the young's first spring, at which <br />time the adolescent birds are driveri from the family group with jabs and lunges before the pair <br />lifts off for the long migration nortll. <br />The central Platte in the Big Bend area of Nebraska is made up of alluvial bottomlands, <br />river terraces, and gently rolling bluffs along the river escarpment. Bottom lands are flat and <br />extend for up to 15 miles on both sides of the river channel. Rich prairie soils supports a <br />productive agriculture. Each year, this area provides for the needs of millions of migratory <br />birds--cranes, ducks, and geese. Cranes make good use of harvested corn and alfalfa fields, <br />grassland, and unvegetated river sandbars. They feed on cropland grain, obtain invertebrate (e.g. <br />snails and earthworms) food from alfalfa fields and wetland-grasslands. Wet meadows provide <br />both food and areas for courtship ri.tuals Cranes come to the central Platte because it is the only <br />locale in mid-continent that meets a11 their requirements (Currier, Lingle, and Walker 1985: 7): <br />. • <br />. •t? <br />?' `• ?t • ' . <br />. • <br />• • ' <br />• <br />} <br />- <br />? , <br />. <br />. <br />r <br />' <br />? <br />' <br />:- "-- . ' . . <br />?r • .. <br />. <br />. <br />, <br />? <br />, <br />, <br />, <br /> <br />? <br />' •! <br />. ?ti <br />-/, <br />' : <br />lq'` ?L <br />? <br />? ?+c' <br />` <br />. <br />"? ` <br />.??.' <br />---:.:. <br />:.?•; •::?_-?i.: ;:•.:=?; <br />? .....?.?' <br />• .?;n .., <br />? - <br />? <br />?? <br />? <br />'' <br />• <br />`,? <br />,`'a'? <br />:?„?r• <br />? R .L . <br /> ? <br />1938 <br />M Y ??} ?T"' - ?. ???_,..?$? „?•--?-?-`^-°?-°??"'?-?? ?_ <br />?-°,?,?"?''?-`"?.-?.:.'r`.;`---^• ;?. ? ???? ? <br />•'??,`" ???' ,? <br />1969 <br />?R? <br />G-•?1;e,.?': ?T,? ?, u7, ? .,. ...or? <br />4K?• S •?. •LGTi? <br />...M= <br />1982 <br />r??i-x`---, <br />o .ze :s r <br />Mlies <br />1. shallow water-preferably on <br />submerged sandbars surrounded by <br />deeper water. These areas must be <br />surrounded by wide open spaces <br />around the roost- a radius of at least <br />250 yards; <br />2. they need to put on fat-20 to 25 % of <br />their body weight must be put on <br />while on the Platte, both for the <br />journey north and for surviving early <br />days after arrival in the arctic when <br />food is still scarce; <br />3. they need wet meadow complexes <br />adjacent to the Platte-these serve as a <br />source of protein and minerals needed <br />to trigger breeding processes. <br />Much of the traditional wet meadow <br />area upon which these birds depend has been <br />lost to irrigation and river channelization. <br />Despite this, by early March in a typical year <br />half a million sandhill cranes will be packed <br />into 60 miles of river along the central Platte, <br />taking refuge on sandbars in shallow water. <br />Figure 4 <br />Increased Channelization of tlle Platte A major impact of water capture and <br />(Source: Curriier et al. 1985) use has been a reduction of channel width and <br />11