> On Thu, 26 Aug 1999, Herb Curl wrote

> > I understand that increasing Bald Eagle predation on heron rookeries has
> > had a significant effect. Can anyone confirm that?

There is substantial cause for concern about Great Blue Herons in the
Puget Trough. Bald Eagle predation rates are high at nesting colonies
and abandonments of large colonies are occurring at unprecedented levels
(though the history of recording such things is rather short).

Jane Hadley's article in the Times quoted quite a few of the people with
strong concerns. I expressed similiar concerns but the only quote from
me that she used was the one I tried to use to temper some of my other
comments, which was "Great Blue Herons are still a widespread and abundant
bird". I have been doing some thinking about alternate ways to look into
the possibility of a marked decline in the Puget Sound region. The heronry
abandonments are pretty strong evidence in themselves but there needs to
be some corroborating evidence that the lack of production of young is
producing a population decline.

I thought about Christmas Bird Count data but I haven't done any summaries.
The Web Page for this data would make such an analysis relatively easy.

I talked Dave Nysewander of the Puget Sound Ambient Monitoring Program and
he summarized some of their flight census data since 1992. Appears to
show a general downward trend (if you throw out the first year when they
were not very experience - obviously). If I remember right, the high count
was about 1700 herons in 1993 and the last two years the numbers have been
800+. Unfortunately, these surveys are not designed to sample during similar
tide levels so there is a potentially large source of variability produced
by that factor alone.

It's really an important monitoring need.


On Thu, 26 Aug 1999, Tom Foote wrote:

> Jim Pruske knows a volunteer at the Nisqually Wildlife Refuge who
> counted 26 eagles attacking the heron rookery on McAlister
> Creek. He said the eagles cleaned it out..mostly predating on
> the nestlings.

Now, what is this "26" all about? Are we talking about 26 separate attacks
documented over the course of a month or two (reasonable) or 26 individual
eagles attacking in blood-crazed flock (not so reasonable). Since there
is a nesting pair of eagles very close to this heronry, I would be surprised
if any eagles other than the resident pair got much of a chance to get into
that heronry. The resident birds would kill them.

Kelly McAllister