Changes in productivity and contaminants in bald eagles nesting along the lower Columbia River, USA

Abstract

Previous studies documented poor productivity of bald eagles (Haliaeetus leucocephalus) in the lower Columbia River (LCR), USA, and elevated p,p'-dichlorodiphenyldichloroethylene (DDE), polychlorinated biphenyls (PCBs), dioxins, and furans in eagle eggs. From 1994 to 1995, we collected partially incubated eggs at 19 of 43 occupied territories along the LCR and compared productivity and egg contaminants to values obtained in the mid-1980s. We found higher productivity at new nesting sites along the river, yet productivity at 23 older breeding territories remained low and was not different (p = 0.713) between studies. Eggshell thickness at older territories had not improved (p = 0.404), and eggshells averaged 11% thinner than shells measured before dichlorodiphenyltrichloroethane use. Decreases in DDE (p = 0.022) and total PCBs (p = 0.0004) in eggs from older breeding areas occurred between study periods. Productivity was not correlated to contaminants, but DDE, PCBs, and dioxin-like chemicals exceeded estimated no-effect values. Some dioxin-like contaminants in eggs were correlated to nest location, with highest concentrations occurring toward the river's mouth where productivity was lowest. Although total productivity increased due to the success of new nesting pairs in the region, egg contaminants remain high enough to impair reproduction at older territories and, over time, may alter productivity of new pairs nesting near the river's mouth.

Coming to Terms About Describing Golden Eagle Reproduction

“…Previous research , Buck et al 2005) and annual survey results (Isaacs and Anthony 2008) indicated that nesting success and productivity varied along the Columbia River. We compared those parameters by state, river segment and river mile by simple Chi-square tests on frequencies to quantify the differences and locate individual and groups of breeding areas with low productivity.…”

“…The Columbia was the only shared watershed where breeding areas in both states were included in our study area because the Columbia River corridor provided habitat for many nesting pairs, some breeding areas included portions of both states, and we monitored or coordinated monitoring of breeding areas on the Washington side of the river from 1996-2007. In addition, there have been concerns about the effects of environmental contaminants on the Columbia River subpopulation , Buck et al 2005. Watersheds were further subdivided into smaller areas (App.…”

“…Results of those studies indicated that environmental contaminants, particularly DDE (average 9.7 ppm wet mass basis in fresh eggs, n = 17, range = 4.0-20.0 ppm), dioxin (2,3,7,8-TCDD, average 31.98 ppm, n = 5, range = 5.1-61.0 ppm), and PCB's (average 12.7 ppm, n = 17, range = 4.8-26.7 ppm), were a likely cause of low nesting success in the Columbia watershed . A follow-up study of contaminants in eagle eggs was conducted during 1994 and 1995 (Buck et al 2005) and documented decreased levels of those contaminants (DDE average 6.3 ppm wet mass basis in fresh eggs, n = 13, range = 3.5-12.5 ppm; 2,3,7,8-TCDD average 24 ppm, n = 13, range = 18-37 ppm; and PCB's average 5.4 ppm, n = 13, range = 3.4-11.4 ppm). However, levels were still high enough in the mid 1990s to impair reproduction at some breeding areas and productivity at older breeding areas on the lower segment of the river had not improved since the 1980s (Buck et al 2005).…”

Assessing reproductive and endocrine parameters in male largescale suckers (Catostomus macrocheilus) along a contaminant gradient in the lower Columbia River, USA

“…At sites furthest downstream on the LCR, sperm quality values in LSS were the lowest. Along a similar stretch of the LCR, the lowest bald eagle nest productivities were found at the river's mouth, where the highest concentrations of organochlorines in eggs occurred (Buck et al, 2005). Most PBDE are hydrophobic, lipophilic, and have half-lives on the order of 1-20 years or more.…”

“…In the North Pacific Ocean, adults can bioaccumulate persistent organic pollutants which are then biotransported into freshwater by the migrating fish, their roe, and later their degrading carcasses. During the migration, organohalogens are transferred from fat to muscle (Cullon et al, 2009;Svedsen et al, 2007), which can then be consumed by foraging biota (Ewald et al, 1998) including bald eagles (Haliaeetus leucocephalus) (Buck et al, 2005), great blue herons (Ardea herodias) (Thomas and Anthony, 1999), and osprey (Pandion haliaetus) (Henny et al, 2011). Along the LCR, spatial differences exist in the concentrations of persistent organic pollutants as shown by PBDE concentrations in osprey eggs (Henny et al, 2011).…”