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Camping Impacts Wildlife including Bald Eagles

Many people like to spend their vacations in the wildness where they hope to have encounters with wildlife. But according to a study published in Ecological Applications, that relaxing trip may be quite stressful for wildlife such as bald eagles.

Researchers Robert Steidl of the University of Arizona and Robert Anthony of Oregon State University wanted to assess the effects that increased recreation in wilderness areas would have on the populations of eagles living along the Gulkana National Wild River in south central Alaska. Many visitors come to the area for whitewater boating, fishing and hunting, since the river is one of the few wilderness rivers in Alaska which is accessible by road. In addition, its proximity to two large cities and its abundant populations of sport fish make it an increasingly popular vacation destination for those seeking a vacation in the wilderness.

During their earlier work the researchers noticed that nearly all human usage of the area occurred along the river corridor. Since most eagle pairs in the area nest and forage along the river, the potential for conflict between eagles and humans seemed high.

For four years Steidl and Anthony detailed nesting activities of eagles during 48 hour periods, 24 hours with a small group of people camped near eagle nests and 24 hours with no one camped near nests. The researchers recorded a series of measurements describing eagle behavior along the river, including the amount of time the adults spent brooding and feeding their young, maintaining their nests, preening, perching, sleeping, and vocalizing.

The results of their work provide staggering numbers - humans camped near nests caused a pronounced change in the way adult eagles spent their time. Adult eagles decreased some activities by as much as 59 per cent per day when humans were nearby. In addition, the percentage of time that they left their nesting area unattended increased by 24 per cent.

Some of these decreases may be having direct effects on the survival of nestling eagles, say the researchers. For instance, when humans were near the nests, the number of feeding bouts at the nest decreased by 20 per cent per day. Further, the amount of prey consumed by the eagles decreased by an average of 29 per cent per day.

"Nestlings probably suffered the highest energetic costs from disturbances," says Steidl, "because of their dependence on adults for food." Those losses in energy may have manifested themselves in several ways, he further explains. Growth rates of the eagles could be retarded, for instance, and the eagles' ability to survive the year after fledging may be reduced.

The results of this study are consistent with the findings of other recent research regarding the effects of human activities on breeding birds of prey. The authors of the study warn that assessing the full impact of human activity on wildlife is a difficult process, and full assessment would involve more than just observing and recording the effects that people have on bird reproduction.

"But behaviors such as those observed during our study provide a useful and sensitive tool for gauging the effects of recreational activities on wildlife," says Steidl. "If bird behavior can be carefully quantified, then management strategies can be developed before these and other potentially harmful activities result in long-term negative consequences to bird populations."