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Mercury (Hg), a neurotoxic pollutant, can be transported long distances through the atmosphere and deposited in remote areas, threatening aquatic wildlife through methylation and bioaccumulation. Over the last two decades, air quality management has resulted in decreases in Hg emissions from waste incinerators and coal-fired power plants across North America. The common loon (Gavia immer) is an apex predator of the aquatic food web. Long-term monitoring of Hg in loons can help track biological recovery in response to the declines in atmospheric Hg that have been documented in the northeastern USA. To assess spatial patterns and temporal trends in Hg exposure of the common loon in the Adirondack Park of New York State, we analyzed Hg concentrations in loon blood and egg samples from 116 lakes between 1998 and 2016. We found spatially variable Hg concentrations in adult loon blood and feathers across the Park. Loon Hg concentrations (converted to female loon units) increased 5.7% yr -1 from 1998 to 2010 (p = 0.04), and then stabilized at 1.70 mg kg -1 from 2010 to 2016 (p = 0.91), based on 760 observations. Concentrations of Hg in juvenile loons also increased in the early part of the record, stabilizing 2 years before Hg concentrations stabilized in adults. For 52 individual lakes with samples from at least 4 different years, loon Hg increased in 34 lakes and decreased in 18 lakes. Overall, we found a delayed recovery of Hg concentrations in loons, despite recent declines in atmospheric Hg.

The common loon (Gavia immer), a top predator in the freshwater food web, has been recognized as an important bioindicator of aquatic mercury (Hg) pollution. Because capturing loons can be difficult, statistical approaches are needed to evaluate the efficiency of Hg monitoring. Using data from 1998 to 2016 collected in New York's Adirondack Park, we calculated the power to detect temporal changes in loon Hg concentrations and fledging success as a function of sampling intensity. There is a tradeoff between the number of lakes per year and the number of years needed to detect a particular rate of change. For example, a 5% year -1 change in Hg concentration could be detected with a sampling effort of either 15 lakes per year for 10 years, or 5 lakes per year for 15 years, given two loons sampled per lake per year. A 2% year -1 change in fledging success could be detected with a sampling effort of either 40 lakes per year for 15 years, or 30 lakes per year for 20 years. We found that more acidic lakes required greater sampling intensity than less acidic lakes for monitoring Hg concentrations but not for fledging success. Power analysis provides a means to optimize the sampling designs for monitoring loon Hg concentrations and reproductive success. This approach is applicable to other monitoring schemes where cost is an issue.

Habitat degradation resulting from anthropogenic activities can threaten wildlife populations. Even wildlife existing in seemingly pristine areas are at risk of airborne pollutants and urban development. The common loon (Gavia immer), a top-trophic level predator in freshwater aquatic ecosystems, has previously experienced detrimental changes in reproductive success as a result of anthropogenic activities. However, long-term studies and large sample sizes are necessary to ascertain the impacts of various anthropogenic activities on this long-lived species. Using a multi-year dataset, we investigated the effects of multiple biotic and abiotic factors on the probability of adult male and female common loon hatching and fledging success. From 1998-2017, we banded individual loons, collected blood samples to assess mercury (Hg) exposure of the birds, and monitored their reproductive success. Adult female loon hatching success was negatively associated with the amount of rainfall received in a given year while fledging success was positively associated with the amount of shoreline development. Adult male loon hatching success was positively associated with the amount of shoreline development and fledging success was negatively associated with the number of other loon pairs on a lake.

Understanding how migratory animals respond to spatial and temporal variation in habitat phenology is critical for identifying selection pressures and tradeoffs at different life history stages. We examined the influence of breeding habitat phenology on life history timing of the eastern willet (Tringa semipalmata semipalmata) across a latitudinal gradient of breeding sites on the east coast of North America. To describe migration and life history timing, we deployed light-level geolocators on willets at breeding sites in New Jersey, Massachusetts and Maine, USA and evaluated additional data on life history timing and migratory connectivity from previous studies, eBird and band recoveries. Willets from Nova Scotia to Georgia winter exclusively on the Atlantic coast of northern South America and share common stopover sites. The timing of wintering site departure, breeding site arrival, nesting and southbound departure was later for birds breeding at higher latitudes while the duration of all life phases was similar across sites. Regardless of latitude, nesting corresponded with a consistent stage of seasonal salt marsh biomass accumulation and with peak spring temperature acceleration (GDD jerk). Temperature acceleration and salt marsh biomass were closely correlated with each other across the 11° latitudinal gradient we examined and with the timing of nest initiation across the northern 6° of this gradient. For this northern 6° of latitude, these results suggest that the timing of migration and breeding events in the annual cycle of eastern willets is constrained by a phenological "green wave" of spring salt marsh productivity at breeding sites.

Common loons (Gavia immer) are diving waterbirds that are particularly challenging to keep in captivity due to their specific behavioral and physiologic needs, special housing requirements, and susceptibility to stress-related disease. We report a novel method for housing and captive rearing common loon chicks that was developed as part of the first-ever loon translocation effort in southeast Massachusetts, from 2015 to 2017. Thirteen loon chicks were reared in aquatic pens in a natural lake environment, utilizing noninvasive feeding and monitoring techniques that avoided human habituation. Chicks were reared in aquatic pens for 16-28 days before being released onto the lake. All chicks remained clinically normal and were monitored on the lake for up to 4 months following release. At least four of the chicks were subsequently confirmed to have survived to adulthood when they returned to the area in breeding plumage two to 3 years following release. Two of these confirmed adults displayed prolonged territorial pair behavior together, and this is an encouraging early sign that captive-reared individuals may form successful breeding pairs in the future. Because most immature loons remain on the ocean until at least 3 years of age, we expect additional captive-reared loons to return to the release area in subsequent years. These husbandry techniques could be applied to other loon and diving bird species that are notoriously difficult to house in captivity. The novel feeding techniques described here could also be adapted for loon chicks being reared in pools or other traditional captive settings., (© 2020 Wiley Periodicals, Inc.)

Oil spills are a widespread problem in the marine environment and can have extensive acute and chronic adverse impacts to resident and migratory biota. On 19 January 1996, the North Cape oil tanker caught fire and grounded on the coast of Rhode Island resulting in the spill of 828,000 gal (3134 metric tonnes) of home heating oil. It resulted in the estimated death of nearly 2300 birds, including a projected 402 common loons (Gavia immer) and 12 red-throated loons (Gavia stellata). Based on existing demographic data, a resource equivalency analysis (REA) calculated that the total loss, as measured through dead adults and their foregone young over their expected lifetimes, was 2920 discounted loon-years. To generate compensatory loon years, it was initially estimated that 25 common loon nests would need protection from development for 100 years. Following a $3 million settlement with the parties responsible for the spill, we conducted surveys to identify the highest quality breeding loon habitat for protection. Monitoring efforts included 184 loon territories from 2000 to 2009, representing 866 loon territory-years on 70 lakes in four regions of Maine. To evaluate restoration effectiveness, an updated REA was conducted using productivity data collected from these surveys. Results from the updated REA indicated that were these site-specific data available when the REA was originally generated, 70 nests would have been required to offset the lost loon-years - this project permitted the protection of 119 nests. Future REAs should incorporate site specific productivity data whenever possible to most accurately scale restoration to injury. Ranking lake habitat quality further optimizes restoration effectiveness. Our results indicate breeding success was highest on 24-81 ha lakes and that emphasizing protection of lakes with loon territories in this size class is optimal. Our results demonstrate a need for site-specific restoration plans to achieve the greatest restoration benefits., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Mercury (Hg) concentrations in the blood and feathers of five species of migratory marsh birds, Nelson's sparrow (Ammodramus nelson subvirgatus), song sparrow (Melospiiza melodia), swamp sparrow (Melospiza geogiana), red-winged blackbird (Agelaius phoeniceus), and Virginia rail (Rallus limicola), breeding in marshes along the lower Penobscot River, Maine, far exceeded reference concentrations, exceeded concentrations associated with reproductive health, and are the highest Hg concentrations reported to date for several species. Blood Hg concentrations in adult Nelson's sparrows were greatest in 2007, at 6.6μg/gww (geometric mean) and in 2012, at 6.5μg/gww and greatest in red-winged blackbirds in 2012, 8.0μg/gww. Mercury in blood increased with residence time on the contaminated marshes at an estimated rate of 0.04 to 0.07μg/gww per day. Feather mercury concentrations in specific primary, secondary and tail feathers (P1, S2, R6) were strongly associated with exposure location at the time of feather formation. Geometric mean Hg concentrations in primary feathers (P1) reached 39.6μg/gfw in 2010 in Nelson's sparrows. The paper documents the dynamic nature of Hg concentrations in avian blood and feathers, an important consideration in contaminant study design, and the increased risk to marsh birds posed by Hg deposition from upstream sources., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Mercury is a potent contaminant that can disrupt an organism's behavior and physiology, ultimately affecting reproductive success. Over the last 100 years, environmental deposition of anthropogenic sourced mercury has increased globally, particularly in the U.S. Northeast region. Marine birds are considered effective bioindicators of ecosystem health, including persistent marine contaminants. Goodale et al. (2008) found that mercury exposure exceeded adverse effects levels in some marine bird species breeding across the Gulf of Maine. We re-examined mercury contamination in four species identified as effective bioindicators. Compared with the previous sampling effort, inshore-feeding species showed significant increases in mercury exposure, while one pelagic-feeding species remained stable. This suggests that a major shift may have occurred in methylmercury availability in inshore waters of the Gulf of Maine. Understanding environmental mercury trends in the Gulf of Maine, and its significance to marine birds and other taxa will require a dedicated, standardized, long-term monitoring scheme., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

We investigated the relation between environmental mercury exposure and corticosterone concentrations in free-living adult common loons (Gavia immer). We determined blood and feather mercury concentrations and compared them to testosterone, estradiol, and stress-induced plasma corticosterone concentrations. Although neither testosterone nor estradiol correlated with Hg levels, there was a robust positive relation between blood Hg and stress-induced corticosterone concentrations in males, but not in females. The lack of an effect in females may have been due to overall less contamination in females. There were no significant correlations between feather Hg and stress-induced corticosterone in either sex. To help determine whether Hg had a causal effect on corticosterone, we investigated the impact of experimental Hg intake on the corticosterone stress response in captive juvenile loons. Juveniles were subjected to three different feeding regimes: 0, 0.4 and 1.2μg Hg (as MeHgCL)/g wet weight (ww) fish. We then measured baseline and 30min post-solitary confinement stressor corticosterone concentrations. The Hg fed chicks exhibited a decreased ability to mount a stress response. From these data, we conclude that Hg contamination does appear to alter the corticosterone response to stress, but not in a consistent predictable pattern. Regardless of the direction of change, however, exposure to mercury contamination and the resulting impact on the corticosterone stress response in common loons may substantially impact health, fitness and survival., (Copyright © 2017 Elsevier Inc. All rights reserved.)

We synthesize impediments for evaluating effects to seabirds from open ocean hydrocarbon releases. Effects on seabirds from ship discharges, spills, and well blowouts often are poorly detected and monitored far from land. Regulatory regimes for ocean spills can result in monitoring efforts that are not entirely transparent. We illustrate how interdisciplinary technologies address deficits that hamper individual or population level assessments for seabirds, and we demonstrate where emerging technologies might be engaged to bridge gaps in oil spill monitoring. Although acute mortality from direct oil exposure poses the greatest risk to seabirds, other hazards from light-attraction, flaring, collisions, chronic pollution, and hydrocarbon inhalation around oil infrastructure also may induce bird mortality in the deep ocean.

The widespread distribution of mercury (Hg) threatens wildlife health, particularly piscivorous birds. Western North America is a diverse region that provides critical habitat to many piscivorous bird species, and also has a well-documented history of mercury contamination from legacy mining and atmospheric deposition. The diversity of landscapes in the west limits the distribution of avian piscivore species, complicating broad comparisons across the region. Mercury risk to avian piscivores was evaluated across the western United States and Canada using a suite of avian piscivore species representing a variety of foraging strategies that together occur broadly across the region. Prey fish Hg concentrations were size-adjusted to the preferred size class of the diet for each avian piscivore (Bald Eagle=36cm, Osprey=30cm, Common and Yellow-billed Loon=15cm, Western and Clark's Grebe=6cm, and Belted Kingfisher=5cm) across each species breeding range. Using a combination of field and lab-based studies on Hg effect in a variety of species, wet weight blood estimates were grouped into five relative risk categories including: background (<0.5μg/g), low (0.5-1μg/g), moderate (1-2μg/g), high (2-3μg/g), and extra high (>3μg/g). These risk categories were used to estimate potential mercury risk to avian piscivores across the west at a 1degree-by-1degree grid cell resolution. Avian piscivores foraging on larger-sized fish generally were at a higher relative risk to Hg. Habitats with a relatively high risk included wetland complexes (e.g., prairie pothole in Saskatchewan), river deltas (e.g., San Francisco Bay, Puget Sound, Columbia River), and arid lands (Great Basin and central Arizona). These results indicate that more intensive avian piscivore sampling is needed across Western North America to generate a more robust assessment of exposure risk., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Methylmercury contamination of the environment is an important issue globally, and birds are useful bioindicators for mercury monitoring programs. The available data on mercury contamination of birds in western North America were synthesized. Original data from multiple databases were obtained and a literature review was conducted to obtain additional mercury concentrations. In total, 29219 original bird mercury concentrations from 225 species were compiled, and an additional 1712 mean mercury concentrations, representing 19998 individuals and 176 species, from 200 publications were obtained. To make mercury data comparable across bird tissues, published equations of tissue mercury correlations were used to convert all mercury concentrations into blood-equivalent mercury concentrations. Blood-equivalent mercury concentrations differed among species, foraging guilds, habitat types, locations, and ecoregions. Piscivores and carnivores exhibited the greatest mercury concentrations, whereas herbivores and granivores exhibited the lowest mercury concentrations. Bird mercury concentrations were greatest in ocean and salt marsh habitats and lowest in terrestrial habitats. Bird mercury concentrations were above toxicity benchmarks in many areas throughout western North America, and multiple hotspots were identified. Additionally, published toxicity benchmarks established in multiple tissues were summarized and translated into a common blood-equivalent mercury concentration. Overall, 66% of birds sampled in western North American exceeded a blood-equivalent mercury concentration of 0.2 μg/g wet weight (ww; above background levels), which is the lowest-observed effect level, 28% exceeded 1.0 μg/g ww (moderate risk), 8% exceeded 3.0 μg/g ww (high risk), and 4% exceeded 4.0 μg/g ww (severe risk). Mercury monitoring programs should sample bird tissues, such as adult blood and eggs, that are most-easily translated into tissues with well-developed toxicity benchmarks and that are directly relevant to bird reproduction. Results indicate that mercury contamination of birds is prevalent in many areas throughout western North America, and large-scale ecological attributes are important factors influencing bird mercury concentrations., (Published by Elsevier B.V.)

We captured 93 wintering adult and subadult Common Loons (Gavia immer) in coastal Louisiana from 2011 to 2015 following the Deepwater Horizon oil spill. We tested blood samples for exposure to polycyclic aromatic hydrocarbons (PAHs) and measured physiological variables including hematocrit, hemoglobin and total blood protein. PAH concentrations in loon blood differed from year to year and by age class. High PAH concentrations were significantly related to lower body masses in both adult and subadult birds and higher serum protein levels in adults only. PAH concentrations had marginal relations with both hematocrit and hemoglobin levels. The types of PAHs detected also underwent a major shift over time. The PAHs detected in 2011, 2012, and 2015 were primarily low molecular weight (three carbon rings); however, in 2013, most detected PAHs were high molecular weight (four carbon rings). It is unclear what events led to the increase in PAH concentrations and the shift in type of PAHs over time., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A streamlined method has been developed for the isolation and analysis of polycyclic aromatic hydrocarbons in avian blood cells and plasma utilizing quick, easy, cheap, effective, rugged, and safe extraction in combination with novel phospholipid cleanup technology. A variety of traditional extraction and cleanup techniques have been employed in the preparation and analysis of polycyclic aromatic hydrocarbonsin a variety of matrices; liquid-liquid partitioning, solid-phase extractions, gel permeation chromatography, and column chromatography are all effective techniques, however they are laborious and time consuming processes that require large amounts of solvent. Using quick, easy, cheap, effective, rugged, and safe extraction coupled with phospholipid cleanup, samples can be quickly screened while maintaining high throughput and sensitivity. With a liquid chromatography approach, analysis times may be kept short at 16 min while maintaining high analyte recovery. Recoveries in quality control samples ranged from 70 to 109%, with average surrogate recoveries of 80.6 ± 1.10%. The result of using a quick, easy, cheap, effective, rugged, and safe extraction approach in conjunction with phospholipid cleanup is a methodology that significantly reduces sample preparation time and solvent use while maintaining high sensitivity and reproducibility., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The current understanding of methylmercury (MeHg) toxicity to avian species has improved considerably in recent years and indicates that exposure to environmentally relevant concentrations of MeHg through the diet can adversely affect various aspects of avian health, reproduction, and survival. Because fish-eating birds are at particular risk for elevated MeHg exposure, the authors surveyed the available primary and secondary literature to summarize the effects of dietary MeHg on the common loon (Gavia immer) and to derive ecologically relevant toxic thresholds for dietary exposure to MeHg in fish prey. After considering the available data, the authors propose three screening benchmarks of 0.1, 0.18, and 0.4 µg g(-1) wet weight MeHg in prey fish. The lowest benchmark (0.1 µg g(-1) wet wt) is the threshold for adverse behavioral impacts in adult loons and is close to the empirically determined no observed adverse effects level for subclinical effects observed in captive loon chicks. The remaining benchmarks (0.18 and 0.4 µg g(-1) wet wt) correspond to MeHg levels in prey fish associated with significant reproductive impairment and reproductive failure in wild adult loons. Overall, these benchmarks incorporate recent findings and reviews of MeHg toxicity in aquatic fish-eating birds and provide the basis for a national ecological risk assessment for Hg and loons in Canada., (Copyright © 2012 SETAC.)

Much of the Laurentian Great Lakes region is a mercury-sensitive landscape, in which atmospheric deposition and waterborne sources of mercury (Hg) have led to high concentrations of bioavailable methylmercury (MeHg) in predatory fish and piscivorous wildlife. Efforts since the early 1990s have established the common loon (Gavia immer) as the primary avian indicator for evaluating the exposure and effects of MeHg in North America. A regional Hg dataset was compiled from multiple loon tissue types and yellow perch (Perca flavescens), a preferred prey fish species for loons. Hg exposure in loons and perch was modeled to develop male and female loon units (MLU and FLU, respectively), standardized metrics that represent the estimated blood Hg exposure of a male or female loon for a given loon territory or water body. Using this common endpoint approach to assess loon Hg exposure, the authors demonstrate spatial trends in biotic Hg concentrations, examine MeHg availability in aquatic ecosystems of the Great Lakes region in relation to landscape-level characteristics, and identify areas with potentially significant adverse reproductive impacts to loons and other avian piscivores. Based on 8,101 MLUs, seven biological Hg hotspots were identified in the Great Lakes region. Policy-relevant applications are presented.

Anthropogenic inputs of mercury (Hg) into the environment have significantly increased in the past century. Concurrently, the availability of methylmercury (MeHg) in aquatic systems has increased to levels posing risks to ecological and human health. We use the common loon (Gavia immer) as an upper trophic level bioindicator of aquatic Hg toxicity in freshwater lakes. Multiple endpoints were selected to measure potential negative impacts from MeHg body burdens on behavior, physiology, survival and reproductive success. A robust spatio-temporal dataset was used that included nearly 5,500 loon Hg measurements over an 18-year period. We measured significant changes related to elevated MeHg body burdens, including aberrant incubation behavior, lethargy, and wing area asymmetry. Mercury body burdens in adult loons increased an average of 8.4% per year. Increasing Hg body burdens reduced the number of fledged chicks per territorial pair, with highest risk loons producing 41% fewer fledged young than our reference group. Our multiple endpoints establish adverse effect thresholds for adult loons at 3.0 ug/g (wet weight) in blood and 40.0 ug/g (fresh weight) in feathers. Mercury contamination in parts of Maine and New Hampshire is a driving stressor for creating breeding population sinks. Standardized monitoring programs are needed to determine if population sinks occur elsewhere and to track aquatic ecosystem responses to changes in Hg emissions and deposition.

Wild common loons (Gavia immer) were captured across much of their southern North American range. Hematologic and physiologic data were collected to establish reference ranges for adults and chicks from four geographic areas: New England, Canadian Maritimes, south-central Quebec, and the Upper Great Lakes. Mean body mass and blood-glucose levels of adult loons varied among geographic regions. Chicks had lower PCV and total solids than adult loons, and also had faster heart rates and higher blood glucose levels. Although mean body mass in males was consistently greater than in females, hematologic and physiologic reference ranges between sexes were not significantly different. Geographic and age-related differences exist in common loon hematologic and physiologic reference ranges and should be considered when assessing such parameters.

A large data set of over 4,700 records of avian mercury (Hg) levels in northeastern North America was compiled and evaluated. As Hg emissions remain poorly regulated in the United States and Canada, atmospheric deposition patterns and associated ecological responses continue to elicit interest by landscape managers, conservation biologists, policy makers, and the general public. How avian Hg exposure is interpreted greatly influences decision-making practices. The geographic extent and size of this data set is valuable in understanding the factors that affect the exposure of Hg to birds. Featured are differences found among tissues, major aquatic habitats and geographic areas, between age class and gender, and among species. While Hg concentrations in egg and blood reflect short-term Hg exposure, Hg concentrations in liver and feather provide insight into long-term Hg exposure. Blood is a particularly important matrix for relating site-specific exposure to methylmercury (MeHg). The level of MeHg is generally 5-10x greater in adults compared to nestlings. Age also influences MeHg bioaccumulation, particularly for individuals where MeHg intake exceeds elimination. Gender is of interpretive concern when evaluating Hg exposure for species exhibiting sexual dimorphism and niche partitioning. Based on two indicator species, the belted kingfisher (Ceryle alcyon) and bald eagle (Haliaeetus leucocephalus), we found MeHg availability increased from marine, to estuarine and riverine systems, and was greatest in lake habitats. A large sample of > 1,800 blood and egg Hg levels from the common loon (Gavia immer) facilitated a suitable comparison of geographic differences. Although some clusters of highly elevated Hg exposure (i.e., blood levels > 3.0 microg/g, ww and egg levels > 1.3 microg/g, ww) were associated with hydrological and biogeochemical factors known to increase MeHg production and availability, others were not. Geographic areas without a relationship between Hg exposure and biogeochemical processes were associated with emission or waterborne point sources. Differences in Hg exposure among species are primarily correlated with trophic position and availability of MeHg. Although piscivorous species were repeatedly shown to have some of the highest MeHg levels of the 38 species analyzed, insectivorous birds in both aquatic and terrestrial habitats (such as montane areas) were also found with elevated MeHg levels. A better understanding of the factors confounding interpretation of Hg exposure provides an effective basis for choice of indicator species and tissues according to 12 selected scenarios. This and the national need for spatiotemporal monitoring of MeHg availability require careful consideration of indicator species choice. Only then will local, regional, continental, and even global monitoring efforts be effective.

Common loons (Gavia immer) were studied to assess the biomagnification of persistent contaminants in lake ecosystems in Atlantic Canada. Forty-two breeding adults and 20 juvenile loons were captured in August, 1995-1997 on lakes in four areas of southern New Brunswick (Lepreau and Fundy National Park) and Nova Scotia (Halifax and Kejimkujik National Park). Blood samples were collected for analysis of mercury, methylmercury, lead, and selenium. Plasma samples from adult loons were analyzed for PCB congeners and organochlorine pesticides. Secondary flight feathers were collected from adult loons for mercury analysis. Kejimkujik loons had significantly higher geometric mean concentrations of mercury in blood (adults: 5.5 microg/g, wet wt) and feathers (adults: 15 microg/g, fresh wt), and higher levels of PCBs, DDE, oxychlordane, trans-nonachlor, mirex and hexachlorobenzene than loons at Halifax or Lepreau. Blood selenium levels were lowest in Kejimkujik loons. Selenium and mercury concentrations were negatively related in blood of adults across all sites. Adult males had higher concentrations of mercury in blood and feathers and PCBs, DDE, and oxychlordane in plasma, and lower levels of selenium in blood, than adult females. Juvenile loons had lower blood mercury and selenium concentrations than adults. Several contaminants showed significant inter-lake variation within the study sites. Mean blood mercury concentrations in Kejimkujik loons are the highest found in breeding common loons across North America. Of adult loons at Kejimkujik, 92% had blood mercury levels > 4 microg/g (wet wt), which have been associated with impaired reproduction, elevated corticosterone levels, asymmetry in plumage development, and altered breeding behavior in loons there and elsewhere.

While large-scale oil spills can cause acute mortality events in birds, there is increasing evidence that sublethal oil exposure can trigger physiological changes that have implications for individual performance and survival. Therefore, improved methods for identifying small amounts of oil on birds are needed. Because ultraviolet (UV) light can be used to identify thin crude oil films in water and on substrate that are not visually apparent under normal lighting conditions, we hypothesized that UV light could be useful for detecting small amounts of oil present on the plumage of birds. We evaluated black skimmers (Rynchops niger), brown pelicans (Pelecanus occidentalis), clapper rails (Rallus crepitans), great egrets (Ardea alba), and seaside sparrows (Ammodramus maritimus) exposed to areas affected by the Deepwater Horizon oil spill in the Gulf of Mexico as well as from reference areas from 20 June, 2010 to 23 February, 2011. When visually assessed without UV light, 19.6% of birds evaluated from areas affected by the spill were determined to be oiled (previously published data), whereas when examined under UV light, 56.3% of the same birds were determined to have oil exposure. Of 705 individuals examined in areas potentially impacted by the spill, we found that fluorescence under UV light assessment identified 259 oiled birds that appeared to be oil-free on visual exam, supporting its utility as a simple tool for improving detection of modestly oiled birds in the field. Further, UV assessment revealed an increase in qualitative severity of oiling (approximate % of body surface oiled) in 40% of birds compared to what was determined on visual exam. Additionally, black skimmers, brown pelicans, and great egrets exposed to oil as determined using UV light experienced oxidative injury to erythrocytes, had decreased numbers of circulating erythrocytes, and showed evidence of a regenerative hematological response in the form of increased reticulocytes. This evidence of adverse effects was similar to changes identified in birds with oil exposure as determined by visual examination without UV light, and is consistent with hemolytic anemia likely caused by oil exposure. Thus, UV assessment proved useful for enhancing detection of birds exposed to oil, but did not increase detection of birds experiencing clinical signs of anemia compared to standard visual oiling assessment. We conclude that UV light evaluation can help identify oil exposure in many birds that would otherwise be identified visually as unexposed during oil spill events. [ABSTRACT FROM AUTHOR]

Methylmercury (MeHg) is a global environmental contaminant that poses significant risks to the health of humans, wildlife, and ecosystems. Assessing MeHg exposure in biota across the landscape and over time is vital for monitoring MeHg pollution and gauging the effectiveness of regulations intended to reduce new mercury (Hg) releases. We used MeHg concentrations measured in museum specimen feathers (collected between 1869 and 2014) and total Hg concentrations (as a proxy for MeHg) of feathers sampled from wild birds (collected between 2008 and 2017) to investigate temporal patterns in exposure over approximately 150 years for North American songbirds. For individual species, we found greater concentrations for samples collected post-2000 compared to those collected during historic times (pre-1900) for six of seven songbird species. Mean feather concentrations measured in samples collected post-2000 ranged between 1.9 and 17 times (mean 6.6) greater than historic specimens. The proportion of individual songbirds with feather concentrations that exceeded modeled toxicity benchmarks increased in samples collected after 1940. Only 2% of individual songbirds collected prior to 1940 had feather concentrations greater than 2.4 μg/g (a toxicity benchmark related to a 10% decrease in nest success) compared to 35% of individuals collected post-1940. Many species included in this study have a vulnerable or near-threatened conservation status, suggesting recovery actions are needed to address mercury pollution. [ABSTRACT FROM AUTHOR]

The article discusses the detection of polycyclic aromatic hydrocarbons in common loons wintering off in coastal Louisiana after an oil spill in the Gulf of Mexico in April 2010. Results from an experiment to test loon blood samples show that the concentrations and frequency of the chemical appear to increase among loons annually, but concentrations from petroleum-based petrogenic alkyl polycyclic hydrocarbons were significantly higher than combustion-based pyrogenic polycyclic hydrocarbons.

The article discusses the wildlife criterion values for common loons in Adirondack Park, New York based on a study to determine mercury concentrations in Adirondack lakes, and in blood, feather and egg samples of loons. Study results show that the values obtained were small enough to affect behavior and reproductive activity of loons, thus providing an estimate of reasonable mercury thresholds in lakes. The results will also assist environmental legislators to better protect aquatic ecosystems.

The article discusses the migration pathway of common loons from the state of Louisiana to the province of Saskatchewan in Canada where they breed during the winter season. Based on a pilot study using platform terminal transmitters to track bird sightings, the common loons wintering off Louisiana migrated to Saskatchewan. Conversely, previous research findings also indicate that common loons from breeding areas in Saskatchewan overwinter in several North American sites and the Pacific Ocean.

The article discusses the relationship of body mass of common loons with migration distance, based on a study to examine body mass, tarsal width, and bill length of common loons from satellite tracking data in breeding territories in North America. Study results show that body mass is inversely proportional to migration distance, and differences in body mass between male and female loons increase with decreasing migration distance. Males, for example, were larger than females in coastal areas.

The article discusses the effect of size and retention of territories for yellow-billed loons based on a study using satellite transmitters that quantified the habit limitations of three loon breeding populations in Alaska and Canada. Study results show that the range of territory size corresponded to the size of lakes in the areas, and loons who lost their habitats did not occupy new territories. The study also suggests that the lake sizes suitable for breeding may limit population size.

The article presents a study which examined the impact of mercury exposure on the population of the piscivorous common loon in Adirondack Park, New York. Topics discussed include the spatial distibution of mercury, a model for assessing the long-term effect of mercury on common loon reproduction and growth, and the extent of mercury contamination of aquatic ecosystems in the area.

The article discusses mercury exposure affecting the breeding grounds of yellow-billed loons in Alaska and Canada, based on an experimental study to determine the risks posed by mercury originating from waters in eastern Asia. Study results show that mercury concentrations in blood, feather, and egg tissues from live loons and museum specimens have lowered the species' productivity. Findings also indicate that mercury is an environmental stressor for yellow-billed loons in the Arctic habitats.

Western North America is a region defined by extreme gradients in geomorphology and climate, which support a diverse array of ecological communities and natural resources. The region also has extreme gradients in mercury (Hg) contamination due to a broad distribution of inorganic Hg sources. These diverse Hg sources and a varied landscape create a unique and complex mosaic of ecological risk from Hg impairment associated with differential methylmercury (MeHg) production and bioaccumulation. Understanding the landscape-scale variation in the magnitude and relative importance of processes associated with Hg transport, methylation, and MeHg bioaccumulation requires a multidisciplinary synthesis that transcends small-scale variability. The Western North America Mercury Synthesis compiled, analyzed, and interpreted spatial and temporal patterns and drivers of Hg and MeHg in air, soil, vegetation, sediments, fish, and wildlife across western North America. This collaboration evaluated the potential risk from Hg to fish, and wildlife health, human exposure, and examined resource management activities that influenced the risk of Hg contamination. This paper integrates the key information presented across the individual papers that comprise the synthesis. The compiled information indicates that Hg contamination is widespread, but heterogeneous, across western North America. The storage and transport of inorganic Hg across landscape gradients are largely regulated by climate and land-cover factors such as plant productivity and precipitation. Importantly, there was a striking lack of concordance between pools and sources of inorganic Hg, and MeHg in aquatic food webs. Additionally, water management had a widespread influence on MeHg bioaccumulation in aquatic ecosystems, whereas mining impacts where relatively localized. These results highlight the decoupling of inorganic Hg sources with MeHg production and bioaccumulation. Together the findings indicate that developing efforts to control MeHg production in the West may be particularly beneficial for reducing food web exposure instead of efforts to simply control inorganic Hg sources. [ABSTRACT FROM AUTHOR]