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Ospreys in Oregon and the Pacific Northwest.

U.S. Department of the Interior 

U.S. Geological Survey 

USGS Fact Sheet 153-02

December 2002

Revised September 2005

Identification:

Dark brown above, white below, with white head and 

prominent dark eye stripe. In flight, crooked wings are 

distinctive. Call is a series of loud, sharp whistles.

Body Size:

Weight: 2.5-4.5 pounds (1,200-1,900 grams); 

wingspan: ~56 inches (142 centimeters).

Distribution: 

Worldwide; in 

Oregon around 

large rivers, 

lakes, estuaries 

and reservoirs.

Legal Status:

Protected under 

Migratory Bird 

Treaty Act of 

1918 (as amended) ; not endangered or threatened under 

U.S. Endangered Species Act. 

Nest Size: 

An average-sized nest measured in Corvallis, Oregon 

weighed 264 pounds (120 kilograms) and was 41 inches 

(104 centimeters) in diameter.

Eggs:

Range 1-4, usually 3; creamy 

white, slightly larger than chicken 

egg, and heavily blotched with dark 

brown; hatch in about 38 days.

Diet:

99+% fish; plunges into water feet 

first using a reversible front talon 

and foot pads with tiny impaling spines (spicules) for 

grasping slippery fish. 

Lifespan:

Maximum 25 years in the wild.

The Osprey.

Class: Aves.

 Order: Falconiformes.

 Family: Accipitridae.

 Genus and species: Pandion haliaetus (Latin, sea eagle). painting © Bart Rulon

osprey image © Bart Rulon

A Bridge to the Wild.

From early April through September each year, famous 

residents grace the small western town of Corvallis, Oregon. 

Two ospreys have become mascots of the town since the pair’s 

arrival in 1994. Their nest, built on a 90-foot power pole near 

the twin bridges over the Willamette River, could be seen by 

many commuters on their way in and out of town. After the 

2002 nesting season, the nest was moved a short distance 

downriver to a constructed nesting platform because sticks 

sometimes dropped from the huge nest onto power lines below 

and caused power outages. At the new location, the pair can 

once again raise a family of young, their general well being 

monitored by the 50,000 residents of the community.

Background.

The osprey, often mistakenly called the fish hawk or fish 

eagle, was first documented in Oregon in 1855. Historically, 

ospreys were reported as numerous, nesting in forested areas 

near water because they favored dead trees or trees with flat or 

dead tops. Ospreys drastically declined in abundance through 

the mid-1970’s as a side effect of pesticide use, but they have 

recovered and become a common nesting species along the 

lower Columbia and Willamette Rivers. Ospreys recently have 

adapted to primarily depend on power poles, cellular towers, 

channel markers, and similar structures for nesting sites 

because suitable natural nest sites (trees) are scarce. The 

number of pairs nesting along the Willamette River between 

Eugene and Portland increased from 13 pairs in 1976 to 78 

pairs in 1993, and increased again to 234 pairs in 2001. 

Elsewhere in North America, osprey populations are following 

the same trend. Unlike most birds of prey, ospreys are tolerant 

of human activities and will build nests on almost any suitable 

structure close to water with an abundant supply of fish.

Breeding

Range
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Ospreys as Biological Indicators.

Why are ospreys good biological indicators of ecosystem 

health?

• long-lived and top predators of

 aquatic food webs.

• 99+% of diet is fish captured near

 the nest site.

• each pair mates for life and returns

 to the same nest annually.

• single nests are often distributed 

 at regular intervals along rivers 

 and sometimes in colonies near 

 estuaries with abundant fish populations.

• often build large, visible nests on accessible structures.

• tolerate short-term disturbance at nest site.

These traits allow researchers to quickly locate nests at 

strategic sites, such as above and below urban areas, industrial 

sites, and dams, and remove a sample egg. The egg serves 

as a snapshot of contaminants in the female osprey’s body at 

the time the egg formed. For example, chemical analysis of 

osprey eggs collected from the Columbia River in 1997 and 

1998 show eggs with higher levels of PCBs came from nests 

below Bonneville Dam. Several years later, a dumpsite of 

electrical equipment containing PCBs was discovered in the 

Columbia River near the dam.

Charles Henny, James Kaiser, and Robert Grove, with the 

U.S. Geological Survey (USGS), initiated detailed studies 

along the Willamette (1993) and lower Columbia River 

(1995) to evaluate contaminants in osprey eggs and determine 

if ospreys could be used as biological indicators for long-term 

monitoring of contaminants and general health of rivers. 

Initial studies funded by the USGS Biomonitoring 

Environmental Status and Trends (BEST) Program focused 

on studies of contaminants in fish; however, because the 

biomagnification rate of different contaminants from fish 

to fish-eating birds varies tremendously, ospreys are now 

being tested for the program. Initial findings, based on data 

collected along the Willamette River in 1993, show that some 

contaminants biomagnify from fish to an osprey egg by a 

factor of 200 or more, whereas others show considerably less 

biomagnification. Therefore, data describing contaminant 

residues from fish alone are of limited use in evaluating 

possible contaminant effects on ospreys or other fish-eating 

birds. The biomagnification rate (fish to osprey egg) is critical 

when interpreting the relationship between residue levels in 

fish and effects of contaminants on ospreys. Research is 

underway in Oregon and Washington to better understand 

these relationships. 

Utility company 

workers assist 

USGS scientists in 

collecting an egg 

from a nest.

Osprey Nesting Chronology, Willamette Valley, Oregon. 

Arrival at nest sites ................................20 March - 15 April.

Clutch completion ..................................13 April - 20 May.

Hatching ..................................................21 May - 27 June.

First flight of young ................................15 July - 21 August.

Departure to wintering grounds ..........20 August - 25 September.

Most of the fish (83%) caught by 

osprey in the Willamette River in 1993 were 

largescale suckers, which are numerous and 

undesirable to anglers. Ospreys are able to 

catch these fish (usually in shallow, clear 

water) by hovering and then plunging up to 

3 feet (1 meter) into the water to capture 

the fish. Their dense, oily feathers make 

them well suited to repel water and quickly 

regain flight. The male brings fish to the female 

throughout the incubation and nestling periods, 

and also shares a small portion of the incubation duties. The 

female remains in nearly constant contact with the chicks until 

they are about 35-40 days old. She then leaves the nest more 

often to perch nearby, and occasionally shares hunting duties 

with the male until the chicks are able to fly at about the age 

of 52 days. An osprey pair raising two nestlings consumes 

about 375 pounds (170 kilograms) of fish during the breeding

season. This means that the 234 pairs found along the 

Willamette River in 2001 probably consumed 88,000 pounds 

(40,000 kilograms) of fish during their six-month nesting 

season in Oregon, before they migrated south to wintering 

grounds during late August or September.

Ospreys and Contaminants.

Ospreys are at the top of the aquatic food chain, and are

thus exposed to many pollutants found in the environment. 

Toxic chemicals are present in water, air, sediments, and 

aquatic biota throughout osprey breeding and wintering 

ranges. Many of these contaminants bioconcentrate from 

water passed through fish gills, and bioaccumulate in the fish

from their food. The efficient transfer of chemicals from food

to consumer through two or more trophic levels results in 

biomagnification, a systematic increase in tissue residue 

concentrations from one trophic level to another. Residues of 

some organochlorine insecticides, polychlorinated biphenyls 

(PCBs), dioxins, and furans, have been found in the 

Willamette River and are potentially toxic to fish, wildlife, 

and humans. DDT, a well-known pesticide, breaks down to

form DDE, which causes eggshells to thin and be easily

broken, even under the female’s tender care. Because of 

eggshell thinning, osprey productivity decreased in the 1950’s 

and 1960’s, causing populations to decline dramatically until 

the ban of DDT in 1972. Osprey populations have recovered 

noticeably due to reduced DDE levels in the environment, 

increased respect and appreciation of raptors by the public, and 

their recent adaptation to human-made structures for nest sites.
Photo E

Photo A

Photo F

Photo G

Use of Power Poles.

The rapid osprey population increase along 

the Willamette River during the past decade has 

resulted in about 25 new nesting pairs each year, 

with most nests built at power pole sites (74% of 

occupied nests in 2001). The large stick nests are 

primarily built on top of double-crossarm power 

poles at irrigation pumps in agricultural fields near 

the river. The bulky nests often cause power 

outages when sticks interfere 

with electrical equipment. Also, 

the electrocution potential is 

extreme for ospreys when 

building new nests or perching 

on power poles. This is because 

the osprey’s nearly 5-foot (1.5 

meter) wingspan can complete 

the circuit between either closely 

spaced energized equipment or 

between one energized wire and 

one neutral or ground wire. 

(Photo A). 

Utility companies use several remedial 

actions to resolve power outages and 

electrocution problems while accommodating nesting osprey. Actions include building 

an alternate nesting platform above the 

power pole wires (Photo B) or installing a 

taller, non-energized pole with nesting 

platform nearby (Photo C). Sometimes, 

the nest is left undisturbed and insulated 

jumper wires are added to 

isolate the nest from 

energized wires and 

equipment (Photo D). It 

is important to cover all 

energized equipment at 

or near the nest to prevent 

electrocutions and outages. 

These practices are best 

implemented between 

September 15 and March 31 

to avoid disturbing nesting osprey. Brief visits to the power 

pole nests to trim sticks away from electrical equipment are 

 Osprey Use of Artificial Nest Sites.

helpful in preventing outages during the short term. 

The remedial actions have resulted in a sharp decline

of osprey at unsafe power pole sites during the past 

decade (Figure 1). 

Ospreys readily accept alternate nesting platforms, especially if a few armloads of sticks from 

the old nest are scattered on the new platform. 

Attempts to deter osprey from nesting at a chosen 

site without providing an alternate nesting platform

are rarely successful because 

ospreys have tenacious nest site 

fidelity. Effective nest deterrent 

devices are a vital component of 

any nest relocation project and are 

used to encourage nesting pairs to 

accept the alternate platform 

structure. Several different devices 

have been used in attempts to 

prevent nest building on power 

poles, some of which are more 

effective than others (Photos E 

and F). 

USGS scientists, in collaboration

with local utility companies and the Avian 

Power Line Interaction Committee, are 

evaluating nest management strategies and 

osprey electrocution rates in the Willamette 

Valley. The results should prove valuable for 

managing osprey use of power poles 

for nesting sites throughout the osprey’s 

breeding range. 

Use of Channel Markers

The osprey population has 

also increased along the lower 

286 miles (460 kilometers) of 

the Columbia River. In 1998, 

about 40 percent of approximately 100 occupied osprey 

nests along the river were built 

on channel markers. Some 

of these nests obstructed 

navigation lights. The U.S. 

Coast Guard, which is 

responsible for maintaining navigation structures, 

is accommodating osprey 

by constructing lateral nest 

platforms away from lights 

(Photo G).

Photo D

100 % ______________________

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 80 % ______________________

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 60 % ______________________

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 40 % ______________________

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 20 % ______________________

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Non-energized pole 

 with platform

Energized pole 

 with platform

Energized pole 

 - not modified

Transmission tower

Power Pole Nest Sites

1993

N = 66

2001 

N = 171

Nest Sites Used

Figure 1

Photos B (above) & C (right)
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The annual migration of osprey has been traced from Oregon 

and Washington to various locations in Southern Mexcio and 

Central America.

An osprey fitted with a temporary transmitter for tracking 

its migration via satellite (note: antenna on back).

Suggested reading:

Henny, C.J. and J.L. Kaiser. 1996. Osprey population 

increase along the Willamette River, Oregon, and the role 

of utility structures, 1976-1993. Pp 97-108 in: Raptors in 

Human Landscapes. Academic Press, London.

Henny, C.J., J.L. Kaiser, R.A. Grove, V.R. Bentley, 

J.E. Elliott. 2003. Biomagnification factors (fish to 

osprey eggs from the Willamette River, Oregon, U.S.A.) 

for PCDDs, PCDFs, PCBs and OC pesticides: Environmental Monitoring and Assessment, 84(3):275-315

Martell, M.S., C.J. Henny, P.E. Nye, and M.J. Solensky. 

2001. Fall migration routes, timing, and wintering sites 

of North American ospreys as determined by satellite 

telemetry. Condor 103:715-724.

Poole, A.F. 1989. Ospreys: A Natural and Unnatural 

History. Cambridge University Press, Cambridge.

Credits:

Photos — Courtesy of Bruce Dishaw, Thad Furlong, 

Robert Grove, James Kaiser, and Michael Taft.

Editing — Miranda Ruth.

Graphic Design and Layout — Erik Ackerson.

Osprey Migration Patterns.

Scientists study the migration routes of adult osprey from 

nest sites in western Oregon to wintering grounds by temporarily attaching small transmitters (1.15 ounces; 30-35 grams)

to ospreys and tracking their movements with satellite 

receivers. Members of adult osprey pairs migrate separately 

and winter at different locations, reuniting each spring at the 

nest after a six-month hiatus. Thirteen ospreys have been 

tracked to southern Mexico, one to El Salvador, and one to 

Honduras, each following its own route annually. Many 

osprey winter in coastal areas like Mazatlan and Puerto 

Vallarta. Ospreys nesting in other parts of the United States 

winter farther south into Central and South America. The 

World-Wide Web makes it possible for the results of the 

osprey satellite tracking to be widely available through 

an educational program called “Highway to the Tropics” 

(http://www.raptor.cvm.umn.edu). The program is designed 

for teachers and schoolchildren but has valuable information 

about migrating raptors for anyone interested in the subject. 

A Beneficial Coexistence.

Charismatic, adaptable wildlife that live in close proximity

to humans, like the osprey, motivate people to care about their

natural world. 

Research reveals 

that ospreys can 

warn us of harmful 

environmental 

conditions in and 

near our communities. We can return 

the favor by doing 

what we can to 

make the environment safer for the birds—constructing and maintaining safe, 

appropriate nesting platforms, and keeping our waterways 

clean. This sort of coexistence between wildlife and humans 

contributes to our survival as well as that of other species on 

this planet.

35-40 day-old ospreys

This fact sheet and others are available at 

http://fresc.usgs.gov/. Additional copies available by 

contacting fresc_outreach@usgs.gov or 541-750-1030.

For more information contact :

Charles J. Henny, James L. Kaiser, 

or Robert A. Grove.

 USGS Forest and Rangeland. 

 Ecosystem Science Center.

 3200 SW Jefferson Way. 

 Corvallis, OR 97331.

 phone: 541-757-4840. 

 fax: 541-757-4845.