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33 <br />CHAPTER 3 <br />HABITAT USE BY ENDANGERED AND THREATENED <br />SPECIES ON THE PLATTE RIVER <br />The discussion in this section provi.des the reader with an <br />introduction to the habitats used by whooping cranes, least <br />terns, piping plovers and bald eagles while those species are on <br />the Platte River. Also provided is a•brief description.of how <br />the habitats contribute to satisfying-the life requisites of the <br />species.. A discussion of forage fish habitat is-presented to <br />differentiate warm season and cold season requirements. <br />1. WHOOPING CR.ANE <br />A. Roostincr <br />Whooping crane biologists generally agree that whooping cranes <br />select roost sites based on the security offered by the site(s) <br />which is demonstrated by the following characteristics from Shenk <br />and Armbruster (1986) and USFWS (1987b): <br />(1) Unobstructed channel width (Table 11):- whooping cranes <br />select roost sites free of visual obstructions or with <br />an unobstructed view, presumably to allow them to see <br />approaching terrestrial predators. (2) Presence of water: Whooping cranes roost in water. <br />The availability of water is an inherent-requirement of <br />whooping crane behavior (USFWS 1987a). <br />(3) Depth of water: Whooping cranes generally roost in <br />water less than 18.inches deep. Deeper water was <br />present adjacent to the roost sites measured in the <br />Platte River. Biologists have hypothesized that deep <br />water surrounding riverine roost sites forms a <br />deterrent to.terrestrial predators. <br />(4) Water Width: 7n addition to simply being present and <br />having adequate depths, the expanse of water <br />surrounding the roost site must be sufficiently wide to <br />provide a sense of isolation and security. <br />Shallow portions of river channels are used for raosting by <br />whooping cranes when the species is on the Platte River {USFWS