James D. Paruk

Local Movements of Color-Marked Common Loons

We studied movement of color-marked common loons (Gavia immer) among small lakes (4-349 ha) in northern Wisconsin and the Upper Peninsula of Michigan to determine the frequency, timing, and ecological causes of multiple-lake usage. Most instances of multiple-lake usage fell into 1 of 5 categories: (1) territorial defense of 2 or more lakes by a breeding pair, (2) post-reproductive wandering, (3) territorial shifts prior to breeding, (4) dispersal of displaced breeders, or (5) long-distance movements by young birds. Overall, distances moved by adult loons between lakes were shorter than expected. The frequency of such movements might indicate reconnaissance for new territories, consistent with the frequent territorial takeover observed in this species. Regular use by loons of small clusters of lakes suggests that a management strategy that preserves only small, isolated breeding lakes might be inadequate to sustain nesting pairs and also might hamper natural dispersal between lakes.

Historic and Contemporary Mercury Exposure and Potential Risk to Yellow-Billed Loons (Gavia adamsii) Breeding in Alaska and Canada

Abstract. The Yellow-billed Loon (Gavia adamsii) is one of the rarest breeding birds in North America. Because of the small population size and patchy distribution, any stressor to its population is of concern. To determine risks posed by environmental mercury (Hg) loads, we captured 115 Yellow-billed Loons between 2002 and 2012 in the North American Arctic and sampled their blood and/or feather tissues and collected nine eggs. Museum samples from Yellow-billed Loons also were analyzed to examine potential changes in Hg exposure over time. An extensive database of published Hg concentrations and associated adverse effects in Common Loons (G. immer) is highly informative and representative for Yellow-billed Loons. Blood Hg concentrations reflect dietary uptake of methylmercury (MeHg) from breeding areas and are generally considered near background levels if less than 1.0 µg/g wet weight (ww). Feather (growrn at wintering sites) and egg Hg concentrations can represent a mix of breeding and wintering dietary uptake of MeHg. Based on Common Loon studies, significant risk of reduced reproductive success generally occurs when adult Hg concentrations exceed 2.0 µg/g ww in blood, 20.0 µg/g fresh weight (fw) in flight feathers and 1.0 µg/g ww in eggs. Contemporary mercury concentrations for 176 total samples (across all study sites for 115 Yellow-billed Loons) ranged from 0.08 to 1.45 µg/g ww in blood, 3.0 to 24.9 µg/g fw in feathers and 0.21 to 1.23 µg/g ww in eggs. Mercury concentrations in blood, feather and egg tissues indicate that some individual Yellow-billed Loons in breeding populations across North America are at risk of lowered productivity resulting from Hg exposure. Most Yellow-billed Loons breeding in Alaska overwinter in marine waters of eastern Asia. Although blood Hg concentrations from most breeding loons in Alaska are within background levels, some individuals exhibit elevated feather and egg Hg concentrations, which likely indicate the uptake of MeHg originating from eastern Asia. Feather Hg concentrations tended to be highest in individuals overwintering farthest west (closer to Asia). A retrospective analysis of museum specimens (n = 25) found a two-fold increase in Yellow-billed Loon feather Hg concentrations from the pre-1920s (as early as 1845) to the present. The projected increase in Hg deposition (approximately four-fold by 2050) along with the uncertainty of Hg being released through the thawing of permafrost and Arctic sea ice suggest that Hg body burdens in Yellow-billed Loons may increase. These findings indicate that Hg is a current and potentially increasing environmental stressor for the Yellow-billed Loon and possibly other Nearctic-Palearctic migrant birds.

Polycyclic Aromatic Hydrocarbons Detected in Common Loons (Gavia immer) Wintering off Coastal Louisiana

Abstract. On 20 April 2010, the Deepwater Horizon oil drilling rig located 66 km southeast of the Louisiana coast exploded and, by the time the pipeline was capped in July, estimates of 4.9 million barrels of oil were released in the northern Gulf of Mexico. Polycyclic aromatic hydrocarbons make up a small percentage of petroleum (< 5%), but are the most toxic with known negative impacts on wildlife and humans. Because of their lifestyle and trophic standing, seabirds are often impacted by marine spills. To test for the presence of polycyclic aromatic hydrocarbons, we captured and tested blood in Common Loons (Gavia immer), a winter migrant that spends 4–5 months in the Gulf of Mexico. Common Loons were captured at night, using spotlighting and a large dip net off the Louisiana coast, during January–March in 2011 and 2012. A total of 38 Common Loons were caught and sampled (17 in 2011 and 21 in 2012). Both the concentrations and frequency of polycyclic aromatic hydrocarbons present in Common Loons appear to be increasing between years; however, concentrations were low (< 10 ppb). In 2012, petrogenic alkyl polycyclic aromatic hydrocarbons, those derived from petroleum, were significantly higher than pyrogenic polycyclic aromatic hydrocarbons, derived from combustion and anthropogenic sources. It remains unknown if current levels have any adverse impacts on Common Loon health, reproduction and survival.

Body Mass in Common Loons (Gavia immer) Strongly Associated with Migration Distance

Abstract. During 25 field seasons between 1988 and 2012, Biodiversity Research Institute captured and uniquely color-banded 2,730 adult Common Loons (Gavia immer) on breeding territories in 11 States and seven Provinces throughout North America. Body mass was obtained from each individual; tarsus and bill measurements were obtained from more than half the birds banded. Clinal variation in body mass, tarsal width and bill length was observed. Body mass varied from 2,700 g to 7,600 g; loons from populations in the upper Great Lakes and central Canada were smallest, and size increased to the east and west. Examination of band return and satellite tracking data resulted in three migration distance groups: < 1,500 km; 1,500–3,500 km; and ≥ 3,500 km. Body mass was inversely related to migration distance. Males were significantly larger (> 20%) than associated females, and withinpair differences increased with decreasing migration distance (i.e., males from coastal States were proportionally larger than their mates compared to interior State pairs).

Polycyclic aromatic hydrocarbons in blood related to lower body mass in common loons

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.

Common Loons (Gavia immer) Wintering off the Louisiana Coast Tracked to Saskatchewan during the Breeding Season

Abstract. Common Loon (Gavia immer) migration pathways have been previously identified using resightings, band recoveries, and satellite tracking with platform terminal transmitters, but there remains much to be learned. No band recoveries or resightings of Common Loons from Louisiana have been documented to date, and it is unclear where Common Loons from this region migrate and breed. On 29 March 2011, as part of a pilot study, we implanted two platform terminal transmitters in Common Loons wintering off the Louisiana coast. Both individuals migrated to Saskatchewan, Canada. Previous research using satellite telemetry on migrating Common Loons in the western USA states (Nevada and Montana) showed they migrated to Saskatchewan, but wintered at Lake Mead, Nevada, the Gulf of California and the Pacific Ocean. Our findings are of interest as Common Loons from the same breeding area in Saskatchewan overwinter in different regions of North America.

Winter site fidelity and winter movements in Common Loons (Gavia immer) across North America

ABSTRACT In many avian species, breeding site fidelity has been more thoroughly investigated than winter site fidelity, yet the latter may have a greater impact on survivorship. The Common Loon (Gavia immer) is an example of a species whose breeding site fidelity has been well established, but whether it exhibits winter site fidelity remains unknown. Because Common Loons primarily winter in marine waters off coastal shores, winter site fidelity has been challenging to document. We investigated winter site fidelity in Common Loons across North America using satellite transmitters, recaptures, and resightings of previously color-marked individuals. Color-marked adults returned in consecutive years to the same coastal wintering locations in California, Washington, Louisiana, Maryland, and Massachusetts, USA. We estimated adult annual apparent survival as 77% (0.48–0.93) and adult winter site fidelity as 85% (0.35–0.98). This finding has important conservation implications in the aftermath of recent marine oil spills; if Common Loons return to the same contaminated wintering areas annually, decreased fitness and survivorship could result in population-level effects.

Hematological indices of injury to lightly oiled birds from the Deepwater Horizon oil spill

Avian mortality events are common following large-scale oil spills. However, the sublethal effects of oil on birds exposed to light external oiling are not clearly understood. We found that American oystercatchers (area of potential impact n = 42, reference n = 21), black skimmers (area of potential impact n = 121, reference n = 88), brown pelicans (area of potential impact n = 91, reference n = 48), and great egrets (area of potential impact n = 57, reference n = 47) captured between 20 June 2010 and 23 February 2011 following the Deepwater Horizon oil spill experienced oxidative injury to erythrocytes, had decreased volume of circulating erythrocytes, and showed evidence of a regenerative hematological response in the form of increased reticulocytes compared with reference populations. Erythrocytic inclusions consistent with Heinz bodies were present almost exclusively in birds from sites impacted with oil, a finding pathognomonic for oxidative injury to erythrocytes. Average packed cell volumes were 4 to 19% lower and average reticulocyte counts were 27 to 40% higher in birds with visible external oil than birds from reference sites. These findings provide evidence that small amounts of external oil exposure are associated with hemolytic anemia. Furthermore, we found that some birds captured from the area impacted by the spill but with no visible oiling also had erythrocytic inclusion bodies, increased reticulocytes, and reduced packed cell volumes when compared with birds from reference sites. Thus, birds suffered hematologic injury despite no visible oil at the time of capture. Together, these findings suggest that adverse effects of oil spills on birds may be more widespread than estimates based on avian mortality or severe visible oiling. Environ Toxicol Chem 2018;37:451-461.

Introduction: An Overview of Loon Research and Conservation in North America

Abstract. A workshop titled The Status of Gavia: Conservation in Black and White was held at the 5th North American Ornithological Conference on 14 August 2012, in Vancouver, British Columbia. The last such North American meeting focused on loons was at the American Ornithologists Union meetings in Minneapolis in 1997. During the interim 15 years, our knowledge of this group of diving birds in North America has increased significantly. From the 2012 workshop, as well as from contributions of authors unable to attend, 15 papers are presented in this special issue under five broad headings: behavior, life history and population ecology, movements and migration, habitat and landscape requirements and contaminants. Some highlights include the first data on sex ratios in Common Loon (Gavia immer) chicks, the first adult survival estimates for Red-throated Loons (G. stellata), and first reports of mercury exposure in Yellow-billed Loons (G. adamsii) from Alaska and Canada. In addition, a new long-distance migration record for the Common Loon, a landscape assessment of Common Loons in Massachusetts, and oil concentrations in loons wintering in Barataria Bay, Louisiana (one of the areas hit hardest by the Deepwater Horizon Oil Spill) are documented. We hope this collection of papers will be useful to researchers and wildlife managers in North America and abroad.

Unusually Large Wintering Flock of Common Loons Foraging in the Gulf of Mexico

Abstract Gavia immer (Common Loon) utilizes freshwater lakes for nesting and breeding, but winters off both US coasts and the Gulf of Mexico in marine habitats. They are primarily piscivorous. In the winter, Common Loons feed predominately as single individuals, but they occasionally form small groups or flocks. The groups likely facilitate greater feeding efficiency. The largest previously reported foraging aggregation of wintering Common Loons was approximately 200 individuals. We report an extremely large wintering flock of >600 loons foraging 17 km from the southern coast of Mississippi. More work is needed to understand the prevalence of larger groups of overwintering loons as well as temporal and spatial factors that might predict their occurrence.