Organochlorine Contamination in Bald Eagle Eggs and Nestlings from the Canadian Great Lakes

Unhatched eggs and plasma samples from prefledged bald eagles (Haliaeetus leucocephalus) from a recovering population in the Canadian Great Lakes Basin were contaminated with organochlorine compounds at levels comparable to those reported for eagle populations in several areas of the United States. PCBs were among the most commonly detected contaminants and occurred at high concentrations in plasma. Plasma PCB concentrations in Lake Erie nestlings were significantly higher than in chicks from Lake Nipigon (0.130 and 0.047 mg/kg wet weight, respectively). Blood levels of mirex were higher in nestlings from Lake Superior compared to those from Lake Erie (0.0012 and 0.0006 mg/kg wet weight, respectively). Migration routes and over-winter locations of avian prey that constitute a part of the bald eagle chick's diet are likely to contribute to these spatial contaminant patterns in plasma. Atmospheric deposition and a cold condensation effect for chlordane compounds may have produced higher levels of these compounds in plasma samples from Lake Superior compared to samples from Lake Erie (0.020 and 0.008 mg/kg wet weight, respectively). Levels of DDE in plasma were generally low, ranging in concentration from 0.02 mg/kg wet weight for lakes Erie and Nipigon to 0.06 mg/kg wet weight for Lake Huron. Concentrations of organochlorines in eaglet plasma remained relatively stable between 1990 and 1996; no significant trends associated with year of sampling were detected. The data from Lake Erie showed no correlation between productivity and plasma levels of PCBs or DDE during this time period. There were no indications that the concentrations of contaminants detected were adversely affecting productivity in Canadian Great Lakes bald eagle populations. Residue levels in eggs from Lake Erie eagle territories were equally or more contaminated than eggs from other highly contaminated environments in the United States such as the Great Lakes and Columbia River estuary. Concentrations of DDE and PCBs in Lake Erie eggs declined significantly between 1974 and 1994. Although dieldrin and chlordane levels showed a similar decline, these relationships were not statistically significant. Mirex concentrations were relatively stable. Eggs from Lake of the Woods were significantly less contaminated than those from Lake Erie (PCBs: 3 and 84 mg/kg wet weight, respectively; DDE: 3 and 24 mg/kg wet weight, respectively). Reproductive success (number of young produced/active nest) remained constant between 1982 and 1996 and productivity is sufficient to maintain an increasing population. The number of active nests has increased during this period indicating that the population is expanding and might be expected to do so until suitable habitat becomes limiting. Reductions in organochlorine levels, reintroduction efforts, immigration from other populations, and changes in habitat quality have likely contributed to the observed growth in the number of breeding pairs. Received: 30 October 1997/Accepted: 10 July 1998     

Contaminant trends in lake trout (Salvelinus namaycush) from the Upper Great Lakes

Contaminant body burdens in lake trout (Salvelinus namaycush) from the Upper Great Lakes have been monitored since 1970 on Lake Michigan and since 1977 and 1978 on Lakes Superior and Huron by United States Environmental Protection Agency (USEPA), Great Lakes National Program Office and U.S. Fish and Wildlife Service (USFWS), Great Lakes Fishery Laboratory. Analysis of the Lake Michigan data shows that mean polychlorobiphenyl (PCB) concentrations declined from a maximum of 22.91 mg/kg in 1974 to 5.63 mg/kg in 1982. Mean total DDT concentrations declined from 19.19 mg/kg in 1970 to 2.74 mg/kg in 1982. The decline in both contaminants closely followed first order loss kinetics. If the current declines continue, PCB concentrations will decline to the U.S. Food and Drug Administration (USFDA) tolerance of 2.0 mg/kg in 1988. Mean total DDT concentrations will fall to the International Joint Commission (IJC) objective of 1.0 mg/kg by 1991. Mean dieldrin concentrations increased significantly from 0.20 mg/kg in 1971 to 0.58 mg/kg in 1979 before declining to 0.21 mg/kg in 1982. The decline from 1979–1982 followed first order loss kinetics. As this decline is not reflected in other species (bloater chubs, smelt) it will require additional years of monitoring to determine if dieldrin concentrations between 1979 and 1982 truly represents a declining trend. The only statistically significant trend other than in Lake Michigan was for total DDT which declined significantly in Lake Superior lake trout. Large data variance and the short time frame covered (1977–1982) interfered with detection of trends on Lakes Superior and Huron.     

Spatial and temporal patterns in mercury contamination in sediments of the Laurentian Great Lakes

Data from recent sediment surveys have been collated and mapped in order to determine the spatial distribution of mercury in sediments across the entire Great Lakes basin. Information from historical surveys has also been collated in order to evaluate temporal trends. Lake Huron (2002) exhibited the lowest mercury concentrations (lakewide average concentration, 0.043 microg/g); Lakes Michigan (1994-1996) and Superior (2000) also exhibited relatively low levels (lakewide averages of 0.088 and 0.078 microg/g, respectively). The western basin of Lake Erie (1997-1998, 0.402 microg/g) and Lake Ontario (0.586 microg/g) exhibited the highest levels. Sources of mercury contamination in Lakes Erie and Ontario are primarily attributed to loadings from historical sources, including chlor-alkali production in the Detroit, St. Clair, and Niagara Rivers. The spatial distributions of mercury in sediments of Lakes Huron and Superior suggest that natural geochemical factors are an influence. Surficial sediment mercury contamination was found to have decreased markedly since the late 1960s and 1970s. Decreases in lakewide average sediment concentrations of mercury over this time period ranged from approximately 25% for Lake Ontario to 80% for Lake Huron.     

Associations between regional differences in polychlorinated biphenyls and dichlorodiphenyldichloroethylene in blood of nestling bald eagles and reproductive productivity

The relationship between regional reproduction rates of bald eagles (Haliaeetus leucocephalus) and concentrations of p.p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and total polychlorinated biphenyls (PCBs) in blood plasma from nestling bald eagles was assessed. Blood was analyzed from 309 nestlings from 10 subpopulations of eagles across the Great Lakes region. Geometric mean concentrations of p,p'-DDE and total PCBs were inversely correlated to the productivity and success rates of nesting bald eagles within nine subpopulations. Nestlings eight weeks of age and older had significantly greater geometric mean concentrations of total PCBs and p,p'-DDE than nestlings less than eight weeks of age. The ability to use measurements of p,p'-DDE and total PCBs in nestling blood to determine the potential impact of these contaminants on adult nesting on a regional scale was demonstrated.     

Mercury Contamination in Idaho Bald Eagles, <Emphasis Type="Italic">Haliaeetus leucocephalus</Emphasis>

Because mercury contamination is potentially threatening to bald eagle (Haliaeetus leucocephalus) populations, we collected molted feathers at nests to determine the level of contamination in bald eagles in the state of Idaho, USA. Eagle feathers contained measurable amounts of cadmium (Cd), chromium (Cr), selenium (Se), lead (Pb), as well as mercury (Hg). Cadmium, Cr, Se, and Pb levels averaged 0.17, 4.68, 2.02, and 1.29 mg/kg dry weight, respectively, and were at or below concentrations indicated as causing reproductive failure in bald eagles. Mercury contamination was found to be the highest averaging 18.74 mg/kg dry weight. Although a concentration of only 7.5 mg/kg dry weight Hg in bird feathers can cause reduced productivity and even sterility, all of the eagles we sampled bred successfully and the population of bald eagles continues to grow annually throughout the state.     

Mercury exposure and reproduction in fish-eating birds breeding in the Pinchi Lake region, British Columbia, Canada

To determine whether Hg from geologic/mining-related sources at Pinchi Lake (BC, Canada) was causing elevated Hg exposure and/or adversely affecting reproduction in fish-eating birds, breeding bald eagles (Haliaeetus leucocephalus) on Pinchi Lake and four nearby reference lakes were sampled for blood and feather Hg concentrations and monitored for reproductive success during the summers of 2000, 2001, and 2002. Eggs of red-necked grebes (Podiceps grisgena) also were collected and analyzed. Mercury levels in species at various trophic levels from Pinchi Lake averaged approximately twice those in the same species from nearby lakes combined, even in the absence of substantial new inputs of Hg to Pinchi Lake over several decades. In Pinchi Lake, Hg concentrations in blood and feathers of eagles and eggs of grebes were significantly higher than those in corresponding samples from reference lakes. However, the mean Hg concentration (0.25 microg/g wet wt) in grebe eggs from Pinchi Lake was substantially lower than accepted threshold levels for reproductive toxicity in most avian species (0.5-1.0 microg/g wet wt). Mercury concentrations in the blood of adult eagles and their chicks were highly correlated (r = 0.91, p = 0.004). Despite elevated Hg exposure in adult eagles nesting on Pinchi Lake (blood Hg concentration, 4.3-9.4 microg/ml), birds appeared to be in good body condition, did not differ significantly in terms of weight from eagles nesting on reference lakes, and exhibited no evidence of obvious abnormal behavior or lack of coordination. Eagle reproductive success and productivity on Pinchi Lake were not significantly different from those on all reference lakes combined (p = 0.483).     

Contaminants in fishes from great lakes-influenced sections and above dams of three Michigan Rivers: III. Implications for health of bald eagles

Recently, there have been discussions of the relative merits of passage of fishes around hydroelectric dams on three rivers (Au Sable, Manistee, and Muskegon) in Michigan. A hazard assessment was conducted to determine the potential for adverse effects on bald eagles that could consume such fishes from above and below dams on the three primary rivers. The hazard assessments were verified by comparing the reproductive productivities of eagles nesting in areas where they ate primarily fish from either above or below dams on the three primary rivers, as well as on two additional rivers in Michigan, the Menominee and Thunder Bay. Concentrations of organochlorine insecticides (OCI), polychlorinated biphenyls (total PCBs), 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ), and total mercury (Hg) were measured in composite samples of fishes from above and below hydroelectric dams on the Manistee and Muskegon Rivers, which flow into Lake Michigan, and the Au Sable River, which flows into Lake Huron. Mean concentrations of OCI, total PCBs, and TCDD-EQ were all greater in fishes from below the dams than in those from above. The hazard assessment indicated that current concentrations of Hg and OCI other than DDT (DDT + DDE + DDD) in fish from neither above nor below dams would present a significant hazard to bald eagles (Haliaeetus leucocephalus). Both total PCBs and TCDD-EQ in fishes from below the dams currently present a significant hazard to bald eagles, since their mean hazard quotients (HQ) were all greater than one.     

Time trends (1983-1999) for organochlorines and polybrominated diphenyl ethers in rainbow smelt (Osmerus mordax) from Lakes Michigan, Huron, and Superior, USA

The U.S. Geological Service Great Lakes Science Center has archived rainbow smelt (Osmerus mordax) collected from the early 1980s to the present. These fish were collected to provide time- and site-dependent contaminant residue data needed by researchers and managers to fill critical data gaps regarding trends and behavior of persistent organic contaminants in the Great Lakes ecosystem. In the present study, data are presented for concentrations of several organochlorine (OC) contaminants in the archived smelt, including DDT, polychlorinated biphenyls (PCBs), toxaphene, and chlordanes in Lakes Michigan and Huron (MI, USA) and in Lake Superior (MN, USA). The trends for all the OCs were declining as a first-order decay over the sampled time series (1983/1985-1993/1999) with the exception of toxaphene in Lake Superior and PCBs at the Charlevoix/Little Traverse Bay site in Lake Michigan. Concentration of the emerging contaminant, polybrominated diphenyl ethers (PBDEs), also was traced from its apparent entry into this ecosystem in approximately 1980 until 1999. Time trends for the PBDEs were increasing exponentially at all sites, with concentration-doubling times varying from 1.58 to 2.94 years.     

Selenium and mercury concentrations in California gulls breeding on the Great Salt Lake, Utah, USA

We examined selenium (Se) and mercury (Hg) concentrations in adult California gulls (Larus californicus) nesting on the Great Salt Lake, Utah, USA, during 2006 and 2007. During 2006, the mean Se concentration (+/- standard error) was 18.1 +/- 1.5 microg/g in blood on a dry-weight basis and 8.1 +/- 0.4 microg/g in liver. During 2007, Se concentrations were 15.7 +/- 1.5 microg/g in blood and 8.3 +/- 0.4 microg/g in liver; Hg concentrations were 2.4 +/- 0.3 microg/g in blood and 4.1 +/- 0.5 microg/g in liver. Gulls collected from a freshwater colony located within the watershed of the Great Salt Lake had similar levels of Se in the blood and liver as gulls collected on the Great Salt Lake but lower Hg concentrations. Body mass of adult gulls was not correlated with Se or Hg concentrations in their blood or liver. Selenium concentration in California gull eggs collected during 2006 was 3.0 +/- 0.10 microg/g. Of 72 eggs randomly collected from Great Salt Lake colonies, only one was infertile, and none of the embryos exhibited signs of malposition or deformities. We examined 100 newly hatched California gull chicks from Great Salt Lake colonies for teratogenesis; all chicks appeared normal. Hence, the elevated Se and Hg concentrations in adult gulls nesting on the Great Salt Lake did not appear to impair gulls' health or reproductive ability.     

A dynamic multimedia environmental and bioaccumulation model for brominated flame retardants in Lake Huron and Lake Erie, USA

Polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) may pose a worldwide pollution problem because of their persistence, long-range transport capability, and predisposition to bioaccumulate. The ubiquitous presence of PBBs and PBDEs has heightened interest in determination of their fate. We report results for a fugacity-based dynamic environmental and bioaccumulation model of the fate of hexabromobiphenyl (hexaBB) discharged into the Saginaw Bay region of Lake Huron, USA. We calculated transient fugacity profiles of hexaBB in Lake Huron and Lake Erie water and sediment during the 1970s, 1980s, and 1990s. The hexaBB concentrations in the environmental compartments were used as inputs for a dynamic bioaccumulation model of Lake Huron and Lake Erie aquatic biota. The model results indicate that the sediment compartments of Lakes Huron and Erie serve as reservoirs for the accumulation and slow transfer of hexaBB to the food web constituents of these lakes. We present bioaccumulation factors (BAFs) and compare the predicted hexaBB concentrations in lake trout from the bioaccumulation model with measurements during the period 1980 to 2000. An uncertainty analysis for this model suggests that errors associated with input parameter uncertainty can be reduced by refining estimates of the sediment degradation half-life of hexaBB. The corroborated PBB model has carryover application for modeling the fate of polybrominated diphenyl ether (PBDE) contaminants in the Great Lakes. By fitting model outputs to field measurement data using the transformed least square fit method, we report estimations of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) emission rates into the Lake Huron and Lake Erie watershed areas.     

Trends of Chlorinated Organic Contaminants in Great Lakes Trout and Walleye from 1970 to 1998

Levels of chlorinated organic contaminants in predator fish have been monitored annually in each of the Great Lakes since the 1970s. This article updates earlier reports with data from 1991 to 1998 for lake trout (Salvelinus namaycush) and (Lake Erie only) walleye (Sander vitreus) to provide a record that now extends nearly 30 years. Whole fish were analyzed for a number of industrial contaminants and pesticides, including polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloroethane (DDT), dieldrin, toxaphene, and mirex, and contaminant trends were quantified using multicompartment models. As in the past, fish from Lakes Michigan, Ontario, and Huron have the highest levels of PCBs, DDT, and dieldrin; Superior has the highest levels of toxaphene; and Ontario has the highest levels of mirex. In the period after curtailment of chemical use, concentrations rapidly decreased, represented by relatively short half-lives from approximately 1 to 9 years. Although trends depend on both the contaminant and the lake, in many cases the rate of decline has been decreasing, and concentrations are gradually approaching an irreducible concentration. For dioxin-like PCBs, levels have not been decreasing during the most recent 5-year period (1994 to 1998). In some cases, the year-to-year variation in contaminant levels is large, mainly because of food-web dynamics. Although this variation sometimes obscures long-term trends, the general pattern of a rapid decrease followed by slowing or leveling-off of the downward trend seems consistent across the Great Lakes, and future improvements of the magnitude seen in the 1970s and early 1980s likely will take much longer.     

Profiles of Great Lakes critical pollutants: a sentinel analysis of human blood and urine. The Great Lakes Consortium.

To determine the contaminants that should be studied further in the subsequent population-based study, a profile of Great Lakes (GL) sport fish contaminant residues were studied in human blood and urine specimens from 32 sport fish consumers from three Great Lakes: Lake Michigan (n = 10), Lake Huron (n = 11), and Lake Erie (n = 11). Serum was analyzed for 8 polychlorinated dioxin congeners, 10 polychlorinated furan congeners, 4 coplanar and 32 other polychlorinated biphenyl (PCB) congeners, and 11 persistent chlorinated pesticides. Whole blood was analyzed for mercury and lead. Urine samples were analyzed for 10 nonpersistent pesticides (or their metabolites) and 5 metals. One individual was excluded from statistical analysis because of an unusual exposure to selected analytes. Overall, the sample (n = 31) consumed, on average, 49 GL sport fish meals per year for a mean of 33 years. On average, the general population in the GL basin consume 6 meals of GL sport fish per year. The mean tissue levels of most persistent, bioaccumulative compounds also found in GL sport fish ranged from less than a twofold increase to that of PCB 126, which was eight times the selected background levels found in the general population. The overall mean total toxic equivalent for dioxins, furans, and coplanar PCBs were greater than selected background levels in the general population (dioxins, 1.8 times; furans, 2.4 times; and coplanar PCBs, 9.6 times). The nonpersistent pesticides and most metals were not identified in unusual concentrations. A contaminant pattern among lake subgroups was evident. Lake Erie sport fish consumers had consistently lower contaminant concentrations than consumers of sport fish from Lake Michigan and Huron. These interlake differences are consistent with contaminant patterns seen in sport fish tissue from the respective lakes; GL sport fish consumption was the most likely explanation for observed contaminant levels among this sample. Frequent consumers of sport fish proved to be effective sentinels for identifying sport fish contaminants of concern. In the larger study to follow, serum samples will be tested for PCBs (congener specific and coplanar), DDE, dioxin, and furans.     

Assessment of exposure risk of polychlorinated biphenyls to interior least terns (Sterna antillarum)

Risk of polychlorinated biphenyl (PCB) exposure and effects were assessed for a colony of federally endangered interior least terns (Sterna antillarum) nesting on the Bitter Lake National Wildlife Refuge (NM, USA). The colony feeds from an area on the Refuge (Hunter Marsh/Oxbow Complex) wherein fish with elevated concentrations of total PCBs have been documented. Concentrations of total PCBs in whole fish averaged 0.94 mg/kg with a maximum concentration of 2.77 mg/kg, wet weight. Estimated daily PCB intake rates by adult birds throughout their 180-d breeding season ranged from <0.01 mg/kg/d to 0.98 mg/ kg/d, yielding hazard quotients that ranged from 0.01 to 21.68. Polychlorinated biphenyls pose a moderate risk to the colony of interior least terns that breed at the Bitter Lake National Wildlife Refuge, but the exposure rate is not likely to threaten their overall breeding success.     

Hepatic Concentrations of Inorganic Contaminants and Their Relationships with Nutrient Reserves in Autumn-Migrant Common Loons at Lake Erie

Common loons (Gavia immer) are piscivorous, high–trophic level feeders that bioaccumulate inorganic contaminants at concentrations that can negatively impact their health and reproduction. Concentrations of inorganic contaminants, especially mercury (Hg), in blood, organs, and muscle have been quantified in common loons on breeding grounds, but these data are limited for migrating loons. We investigated sex- and age-related hepatic concentrations of inorganic contaminants in common loons (n = 53) that died from botulism and were salvaged at a Great Lakes staging area (i.e., Long Point, Lake Erie) during November 2005. We also investigated if hepatic concentrations of inorganic contaminants influenced lipid, protein, and mineral in our sample of migrant common loons. Last, we determined if there was correlation between Hg and selenium (Se). Consistent with data from breeding grounds, mean concentrations of Hg in liver were approximately 2.5 times greater in adult ([`(x)] \bar{x}  = 14.64 ± 16.69 μg g<sup>−1</sup>) compared with juvenile birds ([`(x)] \bar{x}  = 3.99 ± 2.27 μg g⁻¹). Elements detected in liver at potentially harmful levels were Hg and Se, of which lipid reserves varied negatively with Hg concentrations but positively with Se concentrations. In addition, Hg and Se were correlated (r = 0.65) at greater then a demethylation threshold (total Hg ≥ 8.5 μg g⁻¹ dw) but not lower than that. Concentrations of inorganic contaminants did not influence protein and mineral levels in our sample of common loons. Our results suggest that Hg accumulation negatively affects lipid levels in migrant common loons. Results are also consistent with a nontoxic Hg–Se protein complex protecting loons migrating through areas that are relatively Se rich. Although the acquisition of Se during the nonbreeding season may decrease the toxicity of Hg, future research should consider the synergistic Hg–Se effect on reproduction in common loons that migrate through Se-rich locales, such as the Great Lakes.     

Structure of thyroid and adrenal glands in rats fed diets of Great Lakes coho salmon (Oncorhynchus kisutch)

Feral Great Lakes coho salmon (Oncorhynchus kisutch) were fed to Sprague-Dawley rats in order to determine the effects of bioaccumulated xenobiotics on mammalian endocrine physiology and assess the risk of human consumption of Great Lakes salmon. Rats fed coho salmon from Lakes Ontario, Erie, and Michigan had enlarged thyroid glands compared with controls fed Pacific Ocean coho or Rat Chow. The thyroid epithelial cell height was significantly increased in the rats fed Lake Ontario coho for 8 weeks, and the cells in this group, and to a lesser extent in the group fed Lake Michigan coho, contained more mitochondria, rough endoplasmic reticulum, Golgi profiles, and colloid-filled vacuoles than those of controls or rats fed Lake Erie coho. Dietary iodide supplementation to rats fed the Lake Ontario coho diet had no effect on either thyroid weight or thyroid histology, suggesting that the goiter was not due to iodide deficiency. The adrenal glands of rats fed coho from Lakes Erie or Michigan were significantly larger (P < 0.01) than those in all other groups, apparently because of an enlargement of the zonae fasciculata and reticularis. In addition, rats given the Lake Ontario coho diet had markedly dilated sinusoidal spaces in the zonae fasciculata and reticularis of the adrenal cortex and also in the adrenal medulla.     

Herring gulls and great black-backed gulls as indicators of contaminants in bald eagles in Lake Ontario,Canada

In 2000, a pair of bald eagles (Haliaeetus leucocephalus) nested successfully along the shorelines of Lake Ontario in North America for the first time since 1957. However, it is a continuing question whether bald eagles will be able to reproduce successfully as they return to nest on Lake Ontario. Great black-backed gulls (Larus marinus) and herring gulls (L. argentatus) were selected as surrogate species to predict contaminant levels in eggs of bald eagles nesting on Lake Ontario. Because of the suspected overlap in the diets of great black-backed gulls and bald eagles (i.e., fish, gull chicks, and waterfowl), the two species probably occupy a similar trophic level in the Lake Ontario food web and, thus, may have similar contaminant levels. Fresh great black-backed gull and herring gull eggs were collected from three study sites in eastern Lake Ontario in 1993 and 1994 and analyzed for contaminants. Average contaminant levels of dichlorodiphenyldichloroethane (p,p'-DDE), total polychlorinated biphenyls (PCBs), and dieldrin in great black-backed gull eggs were 12.85, 26.27, and 0.27 microg/g, respectively. The mean ratio of contaminant levels in great black-backed gull eggs to contaminant levels in herring gull eggs for these three contaminants was 2.09 (range of means, 1.73-2.38). Predicted levels of contaminants in bald eagle eggs in Lake Ontario would be expected to be similar to the mean levels reported for great black-backed gull eggs. As a comparison, contaminant levels in bald eagle eggs collected from other Great Lakes nesting sites were compared to mean levels reported for herring gull eggs collected from nearby sites in 1986 to 1995. The mean ratio of contaminant levels in bald eagle eggs to contaminant levels in herring gull eggs from these sites for DDE, total PCBs, and dieldrin was 2.40 (range of means, 1.73-3.28). These ratios are very similar to those reported using great black-backed gull eggs, illustrating the apparent similarity in trophic status shared by the two top predator species at these Great Lakes sites. Predicted levels of contaminants in bald eagle eggs at Lake Ontario are similar to levels reported for bald eagles breeding at other Great Lakes sites, suggesting that bald eagles may be able to breed on the shores of Lake Ontario. However, it is unclear at this time what level of breeding success should be expected, given that productivity at other similarly contaminated Great Lakes sites may be below that required to sustain a successful breeding population. The absence of an inland bald eagle population from which bald eagles may begin to colonize the shorelines of Lake Ontario may be delaying initiation of nesting site selection; other factors such as habitat and prey availability would likely not limit reproductive success.     

Plasma to egg conversion factor for evaluating polychlorinated biphenyl and DDT exposures in great horned owls and bald eagles

The benefits of nondestructive sampling techniques, such as plasma sampling, to directly measure contaminant exposure levels in at-risk or protected raptor populations are many. However, such assays are generally inconsistent with the most certain source of toxicity reference values, which are based on feeding studies and quantified as dietary or "in ovo" (egg-based) concentrations. An accurate conversion factor to translate nondestructive plasma-based contaminant concentrations to comparable egg-based concentrations will prove valuable to risk assessors investigating the potential effects of chemical exposures to raptors. We used databases describing the concentrations of total polychlorinated biphenyls (PCBs) in great horned owls (GHO; Bubo virginianus) and total PCBs and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) in bald eagles (Haliaeetus leucocephalus) from the Great Lakes region (Michigan, Wisconsin, USA) to develop a relationship to predict concentrations of PCBs and DDE in eggs. To develop a robust predictive relationship, all of the source data included concentrations of both total PCBs and/or DDE for nestling blood plasma and egg samples collected from within discrete active nesting territories and, in most instances, the same nest. The key characteristics (slope and elevation) of each relationship were tested for differences related to species and geographic region. Predicted variability of relationships were examined and compared to variability associated with natural systems. The results of statistical testing indicate that applying the conversion factors between species (GHO to bald eagle) and among geographic regions yields predicted egg concentrations that are not statistically dissimilar and are within the natural variability observed for residue concentrations among eggs of raptors within species and region.     

Productivity,diet, and environmental contaminants in bald eagles nesting near the Wisconsin shoreline of Lake Superior

Bald eagles (Haliaeetus leucocephalus) nesting in the Apostle Islands National Lakeshore and along the Wisconsin shoreline of Lake Superior produced an average of 0.8 young/occupied nest and had an average nest success of 57% during 1983–1988, compared to 1.3 young/occupied nest and 77% nest success in inland Wisconsin. Contaminant levels in nestling bald eagle carcasses collected from nests near Lake Superior were higher than those collected inland, suggesting local contamination. Prey remains collected at nests consisted of fish (50%); birds, primarily herring gulls (Larus argentatus) (48.4%); and mammals (1.2%). Organochlorine and polychlorinated biphenyl (PCB) residues were present at low levels (DDE: ¯x=0.07 g/g wet wt, PCB:¯x=0.21 g/g wet wt) in fish. Herring gulls contained higher concentrations (DDEx=5.5 g/g wet wt, PCB¯x=16.95 g/g wet wt) and appear to be the major source of elevated contaminant levels in bald eagles nesting near Lake Superior.     

Elemental Profiles in Feather Samples from a Mercury-Contaminated Lake in Central California

Flight feathers from six bird species at Clear Lake, CA were analyzed to determine the extent and distribution of mercury contamination from an abandoned mercury mine and associated levels of 14 other elements. Feather samples were collected from adult and juvenile osprey (Pandion haliaetus), including juvenile osprey from three additional comparison sites; adult western grebes (Aechmophorus occidentalis); adult great blue herons (Ardea herodias); adult mallards (Anas platyrhynchos); adult turkey vultures (Cathartes aura); and juvenile double-crested cormorants (Phalacrocorax auritus). Samples were analyzed by a multielemental x-ray fluorescence method. The osprey from Clear Lake showed significantly elevated mercury concentrations relative to the comparison sites. Different species at Clear Lake had different mercury concentrations based on trophic status; osprey exhibited the highest mercury concentrations and the mallards showed the lowest. Lastly, we quantified differences in elemental concentrations, including mercury, between adult and juvenile osprey from Clear Lake. Elements known to be nutrients, such as sulfur and zinc, did not vary significantly among species or sites. Reproductive success of osprey at Clear Lake was monitored from 1992 to 1996 to determine if osprey reproduction was depressed. During this five-year period, the breeding population grew from 10 to 20 nesting pairs and the average reproductive rate was 1.4 fledglings per nesting attempt. Although the osprey showed the highest mercury levels of any species sampled, their reproduction does not appear to be depressed. Received: 13 August 1997/Accepted: 6 January 1998     

Examination of mercury concentration in the feathers of 18 species of birds in southwest Iran

This paper presents the levels of mercury (Hg) in tail feathers from different species of birds, in southwest Iran (Khuzestan to Persian Gulf). Between April and October 2005, we collected tail feathers from 77 birds belonging to 18 species, mostly raptor birds. The birds were collected for the Museum Natural History, Faculty of Natural Resources and Marine Sciences of Tarbiat Modares University. Hg concentrations were evaluated in relation to taxonomic affiliation and trophic level. Feather Hg concentrations ranged from 0.09 to 2.01 mg/kg dry wt. We found a significant difference in feather Hg concentrations across taxonomic groups (p<0.001) with highest concentrations in common kestrel and saker falcon (Falconidae) (1.87 mg/kg) followed by greater spotted eagle, sparrowhawk, goshawk, griffon vulture, buzzards, marsh harrier (Accipiteridae) and owls (Strigidae). Blue-cheeked bee-eater (Meropidae) had intermediate values, followed by European roller (Coraciidae), and lapwing (Charadiidae), whereas black francolin, see-see patridge and chukar (Phasianidae) (0.18 mg/kg) contained the least amount of Hg. There was a significant difference in feather Hg concentrations in relation to trophic levels, at confidence level of 99% (p<0.001). There was an increased pattern in the amount of mercury from herbivorous birds up to vertebrate predators, so that the amount of mercury in vertebrate predators (1.30 mg/kg) was more than 1.5 times as much of the invertebrate predators (0.7 mg/kg) and more than 6 times as much of the herbivorous birds (0.18 mg/kg). We also measured Hg levels in secondary feathers of raptor birds. Paired samples t-test showed that the concentrations of mercury were significantly higher (p<0.001) in the tail feathers (1.2mg/kg) than secondary (0.71 mg/kg). However, Hg levels are below the range found by other authors to cause behavioral change or reduce reproduction (5mg/kg). It seems that exposure of some birds with mercury for a long time causes their high concentration of mercury.