Mercury in non-breeding sparrows of North Carolina salt marshes

Winder, Virginia L.; Emslie, Steven D.

doi:10.1007/s10646-011-0794-y

Cited by 15 publications

(17 citation statements)

References 39 publications

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“…This, combined with strong site fidelity [31], [32] could lead to the pattern observed in this study. This explanation is consistent with the evidence for a temporal increase in Hg exposure on breeding sites for these species during the same time period as the present study [20]. At this time, neither of these explanations can be discounted, and they need not necessarily be considered mutually exclusive.…”

Section: Discussionsupporting

confidence: 92%

“…MARK models may be accurate in not detecting an effect of Hg on survival in these three species, and the observed effect of Hg on Nelson’s Sparrow capture frequency may be spurious. Hg exposure for the species in this study has consistently been documented to be lower at non-breeding sites compared to breeding sites [11], [12], [18]–[20]. Therefore, it seems likely that this reprieve from comparatively high Hg exposure during the breeding season may play a role in lessening the effects of Hg on adult survival [35].…”

Section: Discussionmentioning

confidence: 59%

“…For example, feather Hg increased between captures in Nelson’s and Seaside Sparrows but not in Saltmarsh Sparrows. Previous work has documented that Saltmarsh Sparrows consistently exhibit higher Hg concentrations compared to other songbirds at shared sites [12], [18]–[20], but it has yet to be determined whether this disparity is caused by differences in prey selection, physiology, or some other variable. Regardless of the mechanism, comparatively high Hg bioaccumulation in Saltmarsh Sparrows appears to result in chronically high feather Hg concentrations that do not change from year to year and are not related between captures.…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, each of these species is of conservation concern [14]–[17]. Previous studies have characterized Hg exposure throughout portions of the ranges of Nelson’s and Saltmarsh Sparrows, reporting higher than expected and geographically variable concentrations of Hg in their tissues [11], [12], [18]–[20]. For these reasons, and because of the environmental concerns already identified for these species [13], [21], [22], further research is needed to determine whether Hg concentrations may pose a threat to these populations [23].…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Mercury and Its Risk in Nelson’s, Saltmarsh, and Seaside Sparrows

Winder

2012

PLoS ONE

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BackgroundNelson’s, Saltmarsh, and Seaside Sparrows (Ammodramus nelsoni, A. caudacutus, and A. maritimus, respectively) depend on marsh and wetland habitats – ecosystems in which mercury (Hg) bioavailability is notoriously high. The purpose of the present study was to address the potential impact of Hg on these species using first primary and breast feathers as non-destructive biomonitoring tools.Methods and Principal FindingsFeathers were sampled from wintering sparrows in North Carolina salt marshes (2006–2010). Feather Hg data were used in three risk analysis components (1) Threshold Component – examined feather Hg with regard to published negative effects thresholds; (2) Hg Dynamics Component – examined Hg in sparrows captured multiple times; and (3) Capture Frequency and Survival Component – tested for links between Hg and return frequency and survival. Threshold Component analyses indicated that Hg concentrations in 42–77% of sampled individuals (breast feather n = 879; first primary feather n = 663) were within the range associated with decreased reproduction in other avian species. Hg Dynamics Component analyses demonstrated that Hg increased between first and second captures for Nelson’s (n = 9) and Seaside Sparrows (n = 23). Capture Frequency and Survival Component analyses detected a negative relationship between Hg and capture frequency in Nelson’s Sparrows (n = 315). However, MARK models detected no effect of Hg on apparent survival in any species.Conclusion and SignificanceThis study indicates that current Hg exposure places a considerable proportion of each population at risk. In particular, 52% of all sampled Saltmarsh Sparrows exhibited first primary feather Hg concentrations exceeding those associated with a >60% reduction in reproductive success in other species. This study reports evidence for net annual bioaccumulation, indicating an increased risk in older individuals. These data can be used to inform future population assessments and management for these species.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 59%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of Mercury and Its Risk in Nelson’s, Saltmarsh, and Seaside Sparrows

Winder

2012

PLoS ONE

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“…However, global increases in circulating mercury have resulted in elevated mercury levels in some vulnerable ecosystems which then accumulates in birds living in these ecosystems. In particular, birds living in bogs, estuaries, and other wetlands are at elevated risk, and average blood mercury levels of 0.05 – 0.9 ppm ww have been reported depending on species and season [7], [12], [13]. Birds living in temperate and tropical high elevation forests may have a moderate risk of mercury accumulation with average blood mercury levels of 0.06 – 0.5 ppm ww [11], [14].…”

Section: Introductionmentioning

confidence: 99%

Mercury Reduces Avian Reproductive Success and Imposes Selection: An Experimental Study with Adult- or Lifetime-Exposure in Zebra Finch

2014

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Mercury is a global pollutant that biomagnifies in food webs, placing wildlife at risk of reduced reproductive fitness and survival. Songbirds are the most diverse branch of the avian evolutionary tree; many are suffering persistent and serious population declines and we know that songbirds are frequently exposed to mercury pollution. Our objective was to determine the effects of environmentally relevant doses of mercury on reproductive success of songbirds exposed throughout their lives or only as adults. The two modes of exposure simulated philopatric species versus dispersive species, and are particularly relevant because of the heightened mercury-sensitivity of developing nervous systems. We performed a dosing study with dietary methylmercury in a model songbird species, the zebra finch (Taeniopygia guttata), at doses from 0.3 – 2.4 parts per million. Birds were exposed to mercury either as adults only or throughout their lives. All doses of mercury reduced reproductive success, with the lowest dose reducing the number of independent offspring produced in one year by 16% and the highest dose, representing approximately half the lethal dose for this species, causing a 50% reduction. While mercury did not affect clutch size or survivorship, it had the most consistent effect on the proportion of chicks that fledged from the nest, regardless of mode of exposure. Among birds exposed as adults, mercury caused a steep increase in the latency to re-nest after loss of a clutch. Birds exposed for their entire lifetimes, which were necessarily the offspring of dosed parents, had up to 50% lower reproductive success than adult-exposed birds at low doses of methylmercury, but increased reproductive success at high doses, suggesting selection for mercury tolerance at the highest level of exposure. Our results indicate that mercury levels in prey items at contaminated sites pose a significant threat to populations of songbirds through reduced reproductive success.

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Impact of flow diversion by run‐of‐river dams on American dipper diet and mercury exposure

Silverthorn

Bishop

Jardine

et al. 2017

Enviro Toxic and Chemistry

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Run-of-river dams produce lower greenhouse gas emissions than large hydropower projects, but there is a paucity of research on their potential ecotoxicological impacts through disruption of natural flow regimes. We used stable isotopes (δ C, δ N, δ S) to reconstruct diet and trace methylmercury in a predatory river-resident passerine, the American dipper (Cinclus mexicanus), at 7 regulated and 6 free-flowing mountain streams in coastal British Columbia, Canada. Assimilated diets were comparable among regulated and unregulated streams, dominated by benthic macroinvertebrates and resident freshwater fish, with negligible contributions from anadromous Pacific salmon. Although invertebrates at unregulated streams were isotopically similar along their gradient, dippers and invertebrates sampled below dams on regulated streams had S-depleted tissues, suggesting increased activity of sulfate-reducing bacteria and more Hg methylation below the dams. Mercury concentrations in dipper blood (417.6 ± 74.1 standard error [SE] ng/g wet wt at regulated streams, 340.7 ± 42.7 SE ng/g wet wt at unregulated streams) and feathers (1564 .6 ± 367.2 SE ng/g dry wt regulated, 1149.0 ± 152.1 SE ng/g dry wt unregulated), however, were not significantly different between stream types. Relative to other passerines across western North America, dippers in these densely forested mountain streams experienced high mercury exposure; and one recently regulated stream supported dippers with mercury concentrations of potential toxicity concern (up to 8459.5 ng/g dry wt in feathers and 1824.6 ng/g wet wt in whole blood). Elevated mercury in dippers is likely attributable to the birds' relatively high trophic position and high regional inorganic mercury deposition; however, biogeochemical conditions in reservoirs of some regulated streams may be contributing to methylmercury production. Environ Toxicol Chem 2018;37:411-426. © 2017 SETAC.

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Mercury in non-breeding sparrows of North Carolina salt marshes

Cited by 15 publications

References 39 publications

Characterization of Mercury and Its Risk in Nelson’s, Saltmarsh, and Seaside Sparrows

Characterization of Mercury and Its Risk in Nelson’s, Saltmarsh, and Seaside Sparrows

Mercury Reduces Avian Reproductive Success and Imposes Selection: An Experimental Study with Adult- or Lifetime-Exposure in Zebra Finch

Impact of flow diversion by run‐of‐river dams on American dipper diet and mercury exposure

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