>There appears to be an interesting sociobiological phenomenon
>occuring here with regard to resource competition (is it space or food on
>the local tideland or ???). Any chance that eagles and herons may be
>natural enemies in the lion/hyena style? Do eagles routinely attack ANY
>other large birds nesting relatively near them? There are still one or
>two adult herons feeding in the Marina area; whether they are the
>survivors is unknown. Commentary, please. Thanks,
>
>Maureen E. Ellis me2 at u.washington.edu Univ of WA and Des Moines, WA

Maureen, from what I've been able to glean, eagles are the *primary* cause
for heronry failure in this area, probably much more significant than human
disturbance. As Bald Eagles have recovered from earlier declines, they are
increasing throughout the region, and a consequence of this might well be
greater and greater problems with heronries. Apparently both small and
large ones can be sufficiently disturbed by eagle presence to fail.

They are certainly not "natural enemies," and I very much doubt if it's
resource competition (although herons and fish eagles do seem to interact
in a competitive way in Africa). It's simply that Bald Eagles are
opportunistic predators that will take anything they can, and nesting
herons are too good to pass up. They are known to prey on eggs and young,
although I haven't heard whether they take adults. The interesting
question to ask is "were herons much less common when eagles were more
common in the region?" I don't think we have any way of answering it, and
perhaps all we can do is watch the consequences of the eagle increase. I
doubt if there will be Bald Eagle control programs, no matter how much
havoc they wreak with the herons, and I can't imagine there's a way to stop
the interaction.

Dennis Paulson, Director phone 206-756-3798
Slater Museum of Natural History fax 206-756-3352
University of Puget Sound e-mail dpaulson at ups.edu
Tacoma, WA 98416