[obol] 2007 Bald Eagle Nest Survey Results (long, but not too long)

[Frank Isaacs]

OBOL -

2007 was a banner year for bald eagles nesting in Oregon. For the first 
time, over 500 nesting pairs were documented (512), and over 500 
nestlings were counted (504). When this project started in 1978, bald 
eagles were relatively rare in the state during the breeding season. 
Now, most popular birding areas are in the home range of one or more 
nesting pairs.

Highlights of the 2007 survey of bald eagle breeding areas in Oregon 
and the Washington portion of the Columbia River Recovery Zone:

* 2007 was the 30th year of our census of bald eagle breeding areas 
(1978-2007) and the 37th year for which we have tabulated data 
(1971-2007) on nesting bald eagles in Oregon (OR) and the Washington 
portion of the Columbia River Recovery Zone (WA).

* 2,424 observations were used to summarize the 2007 survey. 341 
people, including volunteers and representatives of 36 organizations, 
contributed thousands of hours to the effort. We thank all of them! 
Without their help the results would have been much less complete.

* History of bald eagle use has been compiled for 1,480 nest trees and 
2 manmade structures in OR, and 178 nest trees in WA, at 662 breeding 
areas (590 in OR, 72 in WA). Bald eagle nests have been discovered in 
33 of 36 (92%) counties in OR, and 6 of 7 (86%) counties in the WA 
portion of the Columbia River Recovery Zone. Counties in OR currently 
with no known nests are Sherman, Gilliam, Morrow, and Umatilla. There 
are no nests known in the Benton Co., WA portion of the study area.

* 109 previously unknown nests were documented in 2007 (100 in OR, 9 in 
WA); 34 were at 31 previously unknown breeding areas (32 at 29 in OR, 2 
at 2 in WA), and 75 (68 in OR, 7 in WA) were at previously known 
breeding areas.

* 572 of 592 breeding areas surveyed (97%) were occupied (OC) by bald 
eagles (512 of 529 in OR, 60 of 63 in WA). 577 nestlings (504 in OR, 73 
in WA) were observed at 536 OC breeding areas (479 in OR, 57 in WA) 
where nesting outcome was determined. 7,579 eaglets have been reported 
at nests on the study area since 1971 (7,000 in OR and 579 in WA).

* Nesting success was 66% in OR and 70% in WA, resulting in 5-year 
nesting success of 65% in OR and 66% in WA. Young/successful breeding 
pair was 1.59 in OR and 1.83 in WA. Three nestlings were observed at 6 
breeding areas in OR and 3 in WA during 2007.

* Productivity was 1.05 young per occupied (YG/OC) breeding area in OR 
and 1.28 in WA, resulting in 5-year productivity of 1.03 YG/OC breeding 
area for OR and 1.09 for WA. This was the 6th consecutive year that the 
5-year productivity for OR was greater than the Recovery Goal of 1.00 
and the 2nd year that the 5-year productivity for WA surpassed that 
goal.

* Nesting success for Recovery Zones (RZ) with at least 5 OC breeding 
areas was highest in RZ 09 (Blue Mountains) with 1.18 YG/OC breeding 
area, and lowest in RZ 22 (Klamath Basin) with 0.91. Productivity was 
greater than 1.00 YG/OC breeding area for all but RZ 22 (Klamath Basin; 
0.91).

* Net increase in the OR population was 8.9% for 2007. Annual net 
increase averaged 6.9% from 1995-2004. The annual increase for 2005 and 
2006 was 3.4% and 3.1%, respectively. We suspect that the larger 
increase in 2007 was due to increased survey effort, which was promoted 
to cooperators at the beginning of the nesting season.

* The number of occupied bald eagle breeding areas reported in the 
Columbia River RZ (144) was greater than for the Oregon portion of the 
Klamath Basin RZ (136) for the 3rd year in a row. The Klamath Basin RZ 
population increased to a new high of 136 after one year of small 
decline in 2006. Reasons for the 2006 decrease (129 to 126) and 2007 
increase (126 to 136) in the Klamath Basin probably were related to 
survey effort rather than a fluctuating population.  

* Our survey has always been an attempt to monitor all known bald eagle 
breeding areas, including searching for new breeding areas as time 
permitted. During the past 3 years, it became apparent that the 
population was larger and potential habitat covered more area than we 
could monitor with available resources. Since 2002, percent of breeding 
areas surveyed decreased by 3%, and breeding areas with unknown outcome 
increased by 8%, and little time was spent searching suitable habitat 
for new breeding areas. Consequently, our population and productivity 
figures minimums.

* A recently dead adult bald eagle found near Prineville this summer 
was banded at Bates Butte, between Sunriver and LaPine in 1981, making 
the bird 26 years old.

* The bald eagle was removed from the Federal threatened species list 
on 9 July 2007, but is still listed as a threatened species by the 
state of Oregon.

* We have decided that we will not coordinate a complete census of bald 
eagles for the next two years. Instead, we will concentrate on writing 
the results of our 30-year project and see how the Federal and State 
monitoring plans develop.

* Thanks to everyone who has helped with this project. It could not 
have been done without you!

- Frank
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Frank B. Isaacs
24178 Cardwell Hill Dr.
Philomath, OR 97370

Home & Office Phone: 541-929-7154
FAX (call for instructions)
Email: isaacsf at onid.orst.edu

Senior Faculty Research Assistant
Oregon Cooperative Fish & Wildlife Research Unit
Oregon State University
Corvallis, OR
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