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."
