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I I I I I I I I I I I I I I I I I I I There are many factors involved in nest site selection, but certain elements seem to be consistent. A clear flight path to a close point on a beach or a river is important, as well as an open view of the surround ing area. A 1 arge majority of nests are constructed in trees (Call 1978, Snow 1973, Chrest 1964, CDOW 1983b). The tree species selected is not as important as the tree's total height and size, and is characteristically the largest or stoutest in the irrmediate area (Call 1978) . The Colorado Division of \Hldlife (1983), citing work by numerous authors, noted that human disturbance has a negative effect on wintering bald eagles. Human disturbance can cause abandonment of traditional roosting areas. However, disturbance from human activities was more tolerable when humans were at least partially hidden from view by vege- tation (COOW 1983b). Studies of wintering bald eagles by the USBR (1981) indicated that the presence of humans at distances over 2,600 feet usually did not disturb eagles. At distances between 1,500 and 2,600 feet, 13 percent of adults and 32 percent of immatures flew. Individual eagles vary considerably in their tolerance to levels of disturbance during nesting activities. Some become habituated to human activ ity, whi 1 e others are negatively affected. (COOW 1983b). Matheson (1968) found that bald eagles are more sensitive to disturbance during egg laying and incubation than later in the nesting cycle. Fish were the major prey species of bald eagles wintering along the Colorado River in 1979 and 1980, with rabbits, mule deer (Odocoileus hemionus), carrion and ducks being the most important secondary food items (Coleman, 1983). - 34 -