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Understanding how risk factors affect populations across their annual cycle is a major challenge for conserving migratory birds. For example, disease outbreaks may happen on the breeding grounds, the wintering grounds, or during migration and are expected to accelerate under climate change. The ability to identify the geographic origins of impacted individuals, especially outside of breeding areas, might make it possible to predict demographic trends and inform conservation decision-making. However, such an effort is made more challenging by the degraded state of carcasses and resulting low quality of DNA available. Here, we describe a rapid and low-cost approach for identifying the origins of birds sampled across their annual cycle that is robust even when DNA quality is poor. We illustrate the approach in the common loon (Gavia immer), an iconic migratory aquatic bird that is under increasing threat on both its breeding and wintering areas. Using 300 samples collected from across the breeding range, we develop a panel of 158 single-nucleotide polymorphisms (SNP) loci with divergent allele frequencies across six genetic subpopulations. We use this SNP panel to identify the breeding grounds for 142 live nonbreeding individuals and carcasses. For example, genetic assignment of loons sampled during botulism outbreaks in parts of the Great Lakes provides evidence for the significant role the lakes play as migratory stopover areas for loons that breed across wide swaths of Canada, and highlights the vulnerability of a large segment of the breeding population to botulism outbreaks that are occurring in the Great Lakes with increasing frequency. Our results illustrate that the use of SNP panels to identify breeding origins of carcasses collected during the nonbreeding season can improve our understanding of the population-specific impacts of mortality from disease and anthropogenic stressors, ultimately allowing more effective management.

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. Research Highlights: Thirteen loon chicks were reared in aquatic pens in a natural lake, using techniques that avoided human habituation. No mortalities were observed, and at least four chicks were confirmed to have survived to adulthood two to 3 years after release. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the authors discuss the beginnings of loon research and conservation in North America, including papers within the issue that include topics on loon movements and migrations, habitat and landscape requirements, and the impact of environmental contaminants.

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.

ABSTRACT Water-level management is widespread and illustrates how contemporary climate can interact directly and indirectly with numerous biological and abiotic factors to influence reproductive success of wildlife species. We studied common loons, an iconic waterbird sensitive to timing and magnitude of water-level changes during the breeding season, using a before-after-control-impact design on large lakes in Voyageurs National Park (Minnesota, USA), to assess the effect of anthropogenic changes in hydroregime on their nesting success and productivity. We examined multiple competing a priori hypotheses in an information-theoretic framework, and predicted that magnitude of changes in loon productivity would be greater in the Namakan Reservoir, where water-level management was altered to mimic a more natural hydroregime, than in Rainy Lake, where management remained relatively unchanged. We determined outcomes from 278 nests during 2004-2006 by performing boat-based visits every 3-5 days, and measuring hydrologic, vegetative, and microtopographic covariates. Relative to comparably collected data for 260 total loon pairs during 1983-1986, productivity (chicks hatched/territorial pair) increased 95% in the Namakan Reservoir between the 2 time periods. Nest success declined in both lakes over the 2 study periods but less so in the Namakan Reservoir than in Rainy Lake. Flooding was a primary cause of nest failures (though second nests were less likely to flood). Nest predation appears to have increased considerably between the 2 study periods. Top-ranked models suggested that timing of nest initiation, probability of nest flooding, probability of nest stranding, and probability of nest success were each related to 2-4 factors, including date of initiation, timing of initiation relative to peak water levels, changes in the elevation of the nest edge, maximum water-level change between initiation and peak water levels, and maximum water-level change between initiation and nest outcome. The top model for all variables except stranding each garnered ≥82% of total model weight. Results demonstrate that water-level management can be altered to benefit productivity of common loons. However, nuanced interactions between land-use change, invasive species, human development, recreation, climate change, and recovery of top predators may often complicate both management decisions and interpretation of water-level impacts on wildlife. © 2013 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Artificial nesting islands, or rafts, are often deployed in common loon (Gavia immer) breeding territories to decrease negative impacts of mammalian predation and water-level fluctuations on nesting success. The management value of rafts has been demonstrated in other studies; however, no published studies have quantified the use or associated reproductive benefits of rafts on lakes exhibiting water-level fluctuations. These lakes constitute a major portion of loon nesting habitat in New England and the Midwest. We used long-term data sets from loon survey and raft management efforts on lakes with stable (SWL) and fluctuating water levels (FWL) in New Hampshire and Maine, USA, to compare raft-use patterns on both types of lakes. We then modeled the influence of percentage of nesting attempts on rafts, lake fluctuation type, and human development index on nesting success as a function of the number of nesting attempts. Loons used 76% of all rafts for nesting, and initial use patterns were similar between SWL and FWL lakes. Half (51%) of rafts used for nesting were first used during the initial year of deployment and 90% of those used were used by the third year. Based on our model, we would expect to see an 8.6% increase in nesting success associated with each successive categorical increase in raft use (0-33%, 33-60%, 60-100%). Nesting success varied with lake fluctuation type, increasing by 21.4% from FWL to SWL types. Our model estimated a 12.8% decrease in nesting success associated with an increasing human development index. Naturally nesting loons on FWL lakes are likely to display mean nesting success levels lower than those needed to sustain populations. We suggest that natural nesting habitat on lakes with fluctuating water levels during the loon nesting season may constitute an ecological trap warranting consideration of raft management. Findings in this study are germane for managing breeding loon populations, particularly those on reservoirs requiring permits from the Federal Energy Regulatory Commission. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]