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<br />00248~ <br /> <br />The Vaseys Paradise KAS population appears to be relatively large and self-sustaining. More <br />than 40% of the present primary KAS habitat at Vaseys Paradise lies below the pre-dam lO-year <br />flood stage of 3540 m3/s and is new, post-dam habitat. The KAS population has survived <br />numerous larger floods both before and after dam construction. The vegetation and the KAS <br />population will re-colonize the scoured area in ~2 years. <br /> <br />Bald Eagles <br /> <br />Distribution and Abundance <br /> <br />Wintering bald eagles were fIrst observed to congregate in Grand Canyon in the early 1980's and <br />the winter population there increased dramatically after 1985 (Brown et ai., 1989, Brown and <br />Stevens 1991, Brown and Stevens 1992). The wintering bald eagle population has been <br />monitored since 1988, and it occurs primarily in the upper half of the Grand Canyon (in Marble <br />Canyon) and on both Lakes Powell and Mead. Density of the Grand Canyon bald eagles during <br />the winter peak (in late February and early March) ranged from 13 to 24 birds between Glen <br />Canyon Dam and the LCR confluence from 1993 to 1995 (Sogge et al., 1995). A concentration <br />of wintering bald eagles occurs in late February at the mouth of N ankoweap Creek, where bald <br />eagles forage on spawning rainbow trout (Brown et al., 1989, Brown 1993). Eagle density was <br />correlated with trout density in the lower 0.5 km of Nankoweap Creek, and trout density was <br />correlated with tributary stream water temperature (Leibfried and Montgomery 1993). <br />App<frentIy, territorial behavior, but no breeding activity, has been detected in Grand Canyon. <br /> <br />Life Requisites <br /> <br />Bald eagles are opportunistic feeders, preying on fIsh, waterfowl, rabbit and road-killed game <br />(Stahlmaster 1987). Wintering bald eagles frequent rivers, reservoirs and lakes, including <br />western reservoirs (Detrich 1987), and their distribution is dependent on prey availability, perch <br />suitability, weather and human disturbance intensity (Ohmart and Sell 1980, Brown and Stevens <br />1997). <br /> <br />At Nankoweap Creek in Grand Canyon, wintering bald eagles preferentially capture rainbow <br />trout in the shallow creek, rather than in the mainstream where foraging success is low (Brown <br />1993, Sogge et al., 1995). Bald eagles at Nankoweap Creek prefer roosting and feeding areas that <br />are relatively free of vegetation. The eagle population there consists of all age classes, with <br />considerable piracy and other interactions between individuals (Brown and Leibfried 1990, <br />Brown and Stevens 1991). The ease and relative safety offoraging in Nankoweap Creek affords <br />wintering bald eagles at Nankoweap Creek the opportunity to accumulate energy reserves needed <br />for their long, northward migration flights and initiation of nesting. <br /> <br />Bald eagle distribution in Glen and Grand canyons appears to be negatively related to human <br />disturbance (Brown and Stevens 1997). Although bald eagles are widely known as opportunistic <br />foragers, they are rare in the Glen Canyon and uppermost Grand Canyon reaches. Those reaches <br />support the highest intensity of recreation and other human uses, and Brown and Stevens (1991) <br />reported that bald eagles in Grand Canyon are extremely sensitive to human disturbance, often <br />abandoning their foraging sites when human came within 0.5 km. For these reasons, Brown and <br />Stevens (1997) concluded that human disturbance is responsible for the general rarity of bald <br />eagles in the upper reaches. <br />