Nocturnal Behavior of the Common Loon, Gavia immer

Very little is known about nocturnal activity of Common Loons (Gavia immer). Knowledge of both diurnal and nocturnal behavior is needed to gain a complete understanding of their ecology. I used night vision light intensifiers to observe nocturnal behaviors of Common Loons. Results were consistent with the hypothesis that, as visual predators, loons would not forage at night and also that they would spend the majority of their time resting (92%). Loons, however, were just as active locomoting (patrolling) during the night as they were during the day. This suggests daily energy budgets need to be reexamined to incorporate this overlooked aspect of loon behavior. Lastly, loons on large lakes with multiple loon territories spent more time locomoting than loons on lakes that had just a single pair

Effects of Water-Level Management on Nesting Success of Common Loons

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 waterlevel 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 waterlevel 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 \u3e82% 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

An evaluation of roadside habitat in northwestern Illinois

Bibliography: pages [94]-99.There is growing interest, regarding the beneficial aspects of highway right-of-way (ROW) management for wildlife. Although many researchers have shown increased abundance of wildlife in managed ROW plots, few have examined the importance adjacent habitats may have on the productivity of ROW habitat. Moreover, more studies are needed to determine which species will be benefitted or unaffected by the availability of roadside habitat. Bird censuses, nest searches and small mammal sampling were conducted along Illinois Route 5 (111-5) ROW’S in northwestern Illinois (Whiteside County). Only 9 species of birds were recorded within the 111-5 ROW’S during my 2-year study. Of these, only 1 bird, the Red-winged Blackbird, was abundant. Six bird species nested in the ROW. The Red-winged Blackbird, however, made 92.9% of all bird nests. Thus, the 111-5 ROW in northwestern Illinois was not used by a wide array of birds for foraging or nesting. Small mammals, on the other hand, found these areas attractive. Shrub plantings increased the numerical abundance of birds (primarily Red-winged Blackbirds) using ROW’S, but they did not increase bird species richness. Shrub plots had significantly more nests/acre than grass plots (7.13 vs. 3.11, respectively). Grass plots seeded to brome/alfalfa had significantly more birds than fescue seeded ROW’S, but there was no difference with respect to bird species richness between the two types of gound covers. Ideas for future management and research are suggested.M.S. (Master of Science

Bald Eagle Predation on Common Loon Chick

Volume: 111Start Page: 115End Page: 11

Initial indications of polycyclic aromatic hydrocarbon exposure in Saskatchewan common loons

Mercury (Hg) and polycyclic aromatic hydrocarbons (PAHs) are global pollutants known for their toxicity to wildlife. Because of their trophic position, common loons (Gavia immer (Brünnich 1764)) are excellent indicators of environmental quality. In 2014 and 2015, tissue samples of ten adult common loons (plus one recapture) were obtained in Meadow Lake Provincial Park, Saskatchewan, and assessed for Hg and PAH exposure. Blood and feather levels of these contaminants are indicative of exposure during breeding and in wintering areas, respectively. Compared with an international Hg database, blood Hg levels were low (<1 μg/g). In most loons (90.5%, 10 out of 11), blood PAH concentrations were also low (<10 ng/g), but high (120 ng/g) for one individual (9.5% 1 out of 11). Feather PAH concentrations were high (95.9 ng/g and 250.6 ng/g) in two of the four loons (50%) caught in 2015. These data indicate that loons breeding in Meadow Lake Provincial Park were exposed to low levels of Hg; however, some individuals are being exposed to PAHs in both their breeding and wintering locations. The effect of these environmental pollutants on individual loon fitness is unclear, but because of their extreme toxicity in biological systems we suggest that future monitoring in the surrounding region is warranted

Evidence of Subclinical Inflammation Relates to PAH Exposure in Overwintering Common Loons (Gavia immer)

Common Loons (Gavia immer) are migratory, piscivorous waterbirds that exhibit high wintering site fidelity. Forty-three immature loons were captured in 2013, 2015–2017, in southwest coastal Louisiana, an area moderately to heavily exposed to oil from the Deepwater Horizon oil spill of 2010. We analyzed blood from loons to examine associations between exposure to polycyclic aromatic hydrocarbons (PAH) and 25 blood analytes. Overall, 60% (26/43) of the loons had detectable concentrations of PAHs, with an average concentration of 55.3 ± 10.3 ng/g. After controlling for body weight, loons with detectable blood PAHs had higher concentrations of absolute eosinophils, lymphocytes, or monocytes compared to loons without PAH exposure. This study provides evidence of subclinical inflammation in Common Loons wintering in coastal Louisiana and identifies exposure to PAHs as a stressor, raising concern for potential impaired fitness in this population resulting from low-level exposure to PAHs

Leveraging genomics to understand threats to migratory birds.

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

Leveraging genomics to understand threats to migratory birds.

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