Greetings Tweeters,

The Nature Conservancy and the National Park Service are currently monitoring
bald eagles on the Skagit River and have been since 1978. What follows are the
highlights of this work. I hope this sheds some light on some of the questions
I've read in recent postings about Skagit bald eagles.

Eagles were counted at least weekly during the winter between 1978 and 1999 on a
19-km reach of the Skagit River from Rockport to Marblemount, and between 1982
and 1999 on a contiguous 24-km reach from Marblemount to Newhalem. Eagles
typically occur in greatest numbers from mid-December until the end of January,
with the peak concentrated during the first 3 weeks in January. The peak 1-day
count has varied from a low of 77 eagles in 1983-84 to 506 in 1991-92, and now
averages about 310. The number of eagle detections has generally increased
since the first counts were made in 1978, but this trend has not been linear.
Detections increased most rapidly from 1987-92, but have averaged about 36%
below the 1991-92 peak during the last 6 years. These long-term trends have not
been uniform along the river. Eagle detections have continued to increase on
the Marblemount-Newhalem reach, growing from 9% of the total count prior to
1987, to an average of 18% of the total since 1992. Increases in chum spawning
along this reach may have resulted in proportionately greater eagle use of this
area. The size of the Skagit chum salmon run was highly correlated with eagle
detections before 1988 (r = 0.81, P < 0.005). Frequency of peak flow events
(floods) also correlated strongly with eagle detections during this period (r =
-0.81, P < 0.005). Note this was a negative correlation. These relationships
have weakened considerably since 1988. During the last 10 years, eagle numbers
on the Skagit have reflected fluctuations in chum salmon abundance on other
Pacific Northwest rivers used by wintering eagles. Low salmon numbers on
several nearby rivers between 1989-93 coincided with high eagle numbers on the
Skagit. A subsequent rebound in these other salmon runs matches a return to
lower eagle counts on the Skagit. The proportion of subadult eagles in the
Skagit population has declined over the last 2 decades. this is similar to a
decline reported from wintering eagle data in Oregon, and may reflect changes in
the age structure of the regional population in the Pacific Northwest.

We also looked at Christmas Bird Count data from several locations in
southwestern B.C. and counts in Skagit and Whatcom counties and found similar
results. The Falcon Research Group has conducted a raptor survey along the
Skagit River below our study area for approximately the past 10 years. They
also show an overall increase in our wintering eagle population.

Currently, no coordinated bald eagle survey is occurring throughout Puget Sound.
The Mid-winter Bald Eagle Count is no longer conducted in Washington, with the
exception of a few local areas (e.g. Whatcom County area). A Puget Sound /
southwestern B.C. annual survey would greatly increase our ability to detect
true population changes in our region. This could be a 1-day count. It was
interesting to see that when we compared our weekly counts to our 1-day annual
peak counts they were highly correlated (r = 0.91, P < 0.001).

Enough talk about eagles. Today is eagle survey day. Think I will go watch
some eagles.

Robert Kuntz
North Cascades Nat'l Park
Sedro Woolley, WA
mailto:robert_kuntz at nps.gov