At 09:46 AM 2/10/98 -0800, Kelly Mcallister wrote:

>Interesting comments, particularly in view of the results of Mark
Stalmaster's
>research on the Skagit River which found that Bald Eagles were being
>disturbed by bank fishers, driftboat fishers, Eagle-watching rafters, and
>others and that this disturbance was reducing feeding opportunities and
>potentially compromising their survival or their condition going into the
>following breeding season. Now, Dr. Stalmaster is the expert on Bald Eagle
>energetics and food requirements so I would be foolish to argue his
>conclusions. Needless to say, he recommended restrictions of human
>activities on portions of the Skagit to reduce effects to overwintering
>eagles.

>However, Bald Eagles sometimes appear quite oblivious to the things going on
>around them.

Research is really the only way to answer such questions. A few years ago,
I attended a talk by biologists studying the effects of rafting on the
Yellowstone River on the productivity of nesting bald eagles.

The outfitters, when queried, were emphatic in their belief that rafting had
no impact. After all, they see bald eagles perched in trees along the river
every day during spring, summer, and fall, apparently unconcerned with the
rafters floating by.

However, when biologists systematically began recording eagle foraging and
fishing behavior on parts of the river frequented by rafters vs. those
portions
not used by rafters, they found a great deal of difference. It was true that
eagles frequently perched for lengthy periods of the day in trees alongside
those portions seeing heavy rafting use. Also true was the fact that eagles
alongside those portions not used by rafters had very different foraging
patterns,
doing so longer and also at different times of day. It was clear that eagles
avoided fishing the river during those times of day when rafters were present
(it's a heavily controlled river).

It wasn't clear that this was affecting productivity, at least during the
relatively
brief period of study (I think it was just a single season, but may've been
two
or three - this was years ago). However, there were proposals on the table to
increase rafting usuage, and there was legitimate concern over the effects of
having more people using the river over more hours and days during the nesting
season.


- Don Baccus, Portland OR <dhogaza at pacifier.com>
Nature photos, on-line guides, and other goodies at
http://donb.photo.net