Environmental Toxicology and Chemistry publication:


Contaminants and Bald Eagles

Bald Eagles: Productivity and Contaminants Relations

The number of bald eagles (Haliaeetus leucocephalus) nesting along the lower Columbia River has doubled inPhoto - Nestling bald eagles, Aldrich Point, Columbia River Estuary (USFWS). the last six years, yet many of these pairs are not reproducing normally. Productivity averages are well below statewide values for eagles nesting in other areas of Oregon and Washington. While productivity of these eagles is low, nesting success in other areas of the two states is close to the goals established to delist the species from the Federal Endangered Species list.

In 1994-95, we collected bald eagle eggs from nests along the lower Columbia River and evaluated eggshell thickness and analyzed egg contents for organochlorine pesticides, total polychlorinated byphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and the dioxin-like planar PCBs. Bald eagle productivity and egg contaminant results from 1994 to 1995 were compared to a previous study to evaluate changes over time.

We found that recent increases in productivity averages were due to new pairs nesting along the river, yet productivity at 23 older breeding areas remained low and was not different between the two study periods. Eggshells averaged 11 percent thinner than shells measured prior to the use of the pesticide DDT. DDE and total PCB concentrations decreased in eggs from older breeding areas between the two study periods, but concentrations were still above values associated with poor productivity. Dioxin equivalents (TEQs) exceeded estimated no-effect values for bald eagles during both studies.

Although total productivity has increased due to the success of new nesting pairs moving into the region, results indicatePhoto - Adult bald eagle, lower Columbia River (USFWS). that organochlorine contaminants continue to impact the breeding success of lower Columbia River eagles. The greatest impact appears to occur at older breeding territories, which were located predominantly in the lower estuary below river mile 60. Eagles nesting toward the mouth of the river may be at greater risk of exposure to some dioxin-like compounds, and the reproductive success of some new pairs nesting in this area could be impacted in the future. Complete report.

Environmental Toxicology and Chemistry publication:
Changes in Productivity and Contaminants in Bald Eagles Nesting Along the Lower Columbia River, USA

Bald Eagle Hazard Assessment Poster

Fact Sheets:

Previous publications on lower Columbia River bald eagles: