Tree swallow, Tachycineta bicolor, nestlings were collected from 76 sites in the Great Lakes which included multiple sites at 27 Areas of Concern (AOCs) and 12 sites not listed as AOCs from 2010 to 2015. Livers were harvested and analyzed for 21 elements. Mercury concentrations differed among AOCs; however, all livers analyzed had concentrations well within background and generally comparable or lower than most sites outside of the Great Lakes. Mercury, the only element specifically identified in the designation of AOCs, does not seem to pose a threat to birds at any of the AOCs monitored. In contrast, selenium (Se) concentrations were elevated at sites on the southwest shore of Lake Michigan to levels that could be harmful to reproduction. Other toxic elements were elevated at selected AOCs, but the concentrations were not at toxic levels. Multivariate analysis identified concentration pattern differences among 8 AOCs that had 3 or more sites sampled. Of 29 possible AOC comparisons, 11 were significant and clear differences in patterns were evident. Concentration patterns of sites within AOCs appeared closely associated with one another. Additionally, Se was the primary contributor to the differences among the 8 AOCs for 9 of the 11 comparisons.

Contaminant exposure of tree swallows, Tachycineta bicolor, nesting in the Great Lakes basin was assessed in 2010 to 2014. Tree swallow nestlings were collected from 69 sites which included multiple sites at some of the 27 Areas of Concern (AOCs) and at nine non-AOC sites. Polycyclic aromatic hydrocarbon (PAHs), polychlorinated biphenyl (PCBs), and polybrominated diphenyl ether (PBDEs) concentrations were measured in nestling stomach contents. Concentrations of PCBs and PBDEs were measured in nestling carcasses. Perfluorinated compounds (PFCs) were measured in nestling plasma. Pooled dietary concentrations of total PAHs were highest at the Rouge River, MI AOC (1,856 ng/g wet weight) and lowest at White Lake, MI AOC (14 ng/g). Nestling PCB concentrations were highest at Waukegan Harbor, IL AOC (geometric mean = 5,908 ng/g) and lowest at a Green Mountain, MN (7 ng/g), a non-AOC. Nestling PBDE concentrations were highest at Torch Lake, MI AOC (72 ng/g) and lowest at Wild Rice Lake, MN (3 ng/g), a non-AOC. Drainages associated with Wurtsmith Air Force Base, MI (non-AOC) had the highest PFC plasma concentrations (1,649 ng/ml) compared to the lowest concentration at Torch Lake, MI AOC (21 ng/ml). Both PAH and PCB concentrations in nestling stomach contents were significantly correlated with concentrations reported in sediment from AOCs in another study. Concentrations of PCBs in mussels measured at AOCs in another study were also significantly correlated with PCB concentrations in tree swallow nestlings. Both PCB and PBDE concentrations were significantly correlated among diet, nestling carcasses, and sibling eggs measured in a companion study.

During 2010-2014, tree swallow (Tachycineta bicolor) reproductive success was monitored at 68 sites across all 5 Great Lakes, including 58 sites located within Great Lakes Areas of concern (AOCs) and 10 non-AOCs. Sample eggs were collected from tree swallow clutches and analyzed for contaminants including polychlorinated biphenyls (PCBs), dioxin and furans, polybrominated diphenyl ethers, and 34 other organic compounds. Contaminant data were available for 360 of the 1249 clutches monitored. Markov chain multistate modeling was used to assess the importance of 5 ecological and 11 of the dominant contaminants in explaining the pattern of egg and nestling failure rates. Four of 5 ecological variables (female Age, Date within season, Year, and Site) were important explanatory variables. Of the 11 contaminants, only total dioxin and furan toxic equivalents (TEQs) explained a significant amount of the egg failure probabilities. Neither total PCBs nor PCB TEQs explained the variation in egg failure rates. In a separate analysis, polycyclic aromatic hydrocarbon exposure in nestling diet was significantly correlated with the daily probability of egg failure. The eight sites within AOCs which had poorer reproduction when compared to 9 non-AOC sites, the measure of impaired reproduction as define by the Great Lakes Restoration Initiative, were associated with exposure to dioxins and furans, PAHs, or depredation. Only 2 sites had poorer reproduction than the poorest performing non-AOC. Using a classic (non-modeling) approach to estimating reproductive success, 82% of nests hatched at least 1 egg, and 75% of eggs hatched.

Tree swallow (Tachycineta bicolor) eggs and nestlings were collected from 16 sites across the Great Lakes to quantify normal annual variation in total polychlorinated biphenyl (PCBs) exposure and to validate the sample size choice in earlier work. A sample size of 5 eggs or 5 nestlings per site was adequate to quantify exposure to PCBs in tree swallows given the current exposure levels and variation. There was no difference in PCB exposure in 2 randomly selected sets of 5 eggs collected in the same year, but analyzed in different years. Additionally, there was only modest annual variation in exposure, with between 69% (nestlings) and 73% (eggs) of sites having no differences between years. There was a tendency, both statistically and qualitatively, for there to be less exposure in the second year compared to the first year.

Tree swallow (Tachycineta bicolor) eggs and nestlings were collected from 16 sites across the Great Lakes to quantify normal annual variation in total polychlorinated biphenyl (PCBs) exposure and to validate the sample size choice in earlier work. A sample size of 5 eggs or 5 nestlings per site was adequate to quantify exposure to PCBs in tree swallows given the current exposure levels and variation. There was no difference in PCB exposure in 2 randomly selected sets of 5 eggs collected in the same year, but analyzed in different years. Additionally, there was only modest annual variation in exposure, with between 69% (nestlings) and 73% (eggs) of sites having no differences between years. There was a tendency, both statistically and qualitatively, for there to be less exposure in the second year compared to the first year.

Tree swallow, Tachycineta bicolor, nestlings were collected from 60 sites in the Great Lakes which included multiple sites at 27 Areas of Concern (AOCs) and 6 sites not listed as AOCs from 2010 to 2014. Nestlings were measured for ethoxyresorufin-O-dealkylase (EROD) activity, chromosomal damage (DNA CV), and six measures of oxidative stress. Each of these bioindicators was divided into four groups from the highest to lowest values and the groups were compared to contaminant concentrations using multivariate analysis. Nestling contaminant concentrations included polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs), and 17 elements. Alkylated polycyclic aromatic hydrocarbons (aPAHs), parent PAHs (pPAHs) were measured in pooled nestling dietary samples. Sibling egg data including measurements of dioxins and selected pesticides were also included in the analysis. Concentrations of aPAHs, pPAHs, and PCBs, in that order, were the major contributors to the significant differences between the lowest and highest EROD activity groups; the pesticides chlordane, heptachlor, and dieldrin were of secondary importance. PBDEs and PFCs were of lower importance and the remaining pesticides and elements contributed very little. PAH toxic equivalents, dieldrin, heptachlor, and chlordane, in that order, were the major contributors to the difference between the low and the two highest groups of DNA CV; pPAHs and aPAHs were or secondary importance. The four categories of reduced glutathione (GSH) and the ratio oxidized glutathione (GSSG)/GSH were not significantly different. There were significant differences among categories of thiobarbituric acid reacting substances (TBARS), GSSG, total sulfhydryl (TSH), and protein bound sulfhydryl (PBSH); however, the individual categories of low to high values barely differed from one another.

Tree swallow, Tachycineta bicolor, nestlings were collected from 60 sites in the Great Lakes which included multiple sites at 27 Areas of Concern (AOCs) and 6 sites not listed as AOCs from 2010 to 2014. Nestlings were measured for ethoxyresorufin-O-dealkylase (EROD) activity, chromosomal damage (DNA CV), and six measures of oxidative stress. Each of these bioindicators was divided into four groups from the highest to lowest values and the groups were compared to contaminant concentrations using multivariate analysis. Nestling contaminant concentrations included polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs), and 17 elements. Alkylated polycyclic aromatic hydrocarbons (aPAHs), parent PAHs (pPAHs) were measured in pooled nestling dietary samples. Sibling egg data including measurements of dioxins and selected pesticides were also included in the analysis. Concentrations of aPAHs, pPAHs, and PCBs, in that order, were the major contributors to the significant differences between the lowest and highest EROD activity groups; the pesticides chlordane, heptachlor, and dieldrin were of secondary importance. PBDEs and PFCs were of lower importance and the remaining pesticides and elements contributed very little. PAH toxic equivalents, dieldrin, heptachlor, and chlordane, in that order, were the major contributors to the difference between the low and the two highest groups of DNA CV; pPAHs and aPAHs were or secondary importance. The four categories of reduced glutathione (GSH) and the ratio oxidized glutathione (GSSG)/GSH were not significantly different. There were significant differences among categories of thiobarbituric acid reacting substances (TBARS), GSSG, total sulfhydryl (TSH), and protein bound sulfhydryl (PBSH); however, the individual categories of low to high values barely differed from one another.

The Cosumnes River Preserve in the California’s Central Valley contains a mosaic of managed wetlands where conditions may promote high levels of methylmercury bioaccumulation. In order to document potential environmental health risk in these wetlands due to mercury, we analyzed dragonfly larvae, western mosquitofish, and tree swallow eggs collected from wetlands and rice fields of the Preserve from 2011 to 2013.

This dataset includes timber harvest treatments; mercury concentrations in aquatic macroinvertebrates, salamanders, and riparian songbirds; carbon and nitrogen stable isotopes in aquatic macroinvertebrates and salamanders; and Bayesian estimates of food web length, basal resource diversity, and isotopic niche size for individual feeding guilds.

This dataset includes timber harvest treatments; mercury concentrations in aquatic macroinvertebrates, salamanders, and riparian songbirds; carbon and nitrogen stable isotopes in aquatic macroinvertebrates and salamanders; and Bayesian estimates of food web length, basal resource diversity, and isotopic niche size for individual feeding guilds.