Common Loons (Gavia immer) winter primarily in marine coastal areas and utilize a forage base that is poorly defined, especially for offshore areas. Information on dive activity is needed for describing foraging strategies and for inferring prey distribution. Archival geolocator tags were used to determine the wintering locations and dive characteristics of adult Common Loons captured and marked on breeding lakes in Minnesota, Wisconsin, and the Upper Peninsula of Michigan. Among loons that completed fall migration, most wintered in the Gulf of Mexico, with smaller proportions wintering off the southern Atlantic Coast or impoundments in the southeastern United States. Adult Common Loons tended to occupy offshore areas of the Gulf of Mexico and the Atlantic Ocean and, on average, spent about 60% of daylight hours foraging. Dive depths were as deep as 50 m (Gulf of Mexico) and dive characteristics indicated that loons were primarily foraging on benthic prey. Total dive duration, time at maximum depth, and post-dive surface intervals increased with dive depths among wintering Common Loons. Our results are expected to contribute to the understanding of the wintering ecology of Common Loons and be useful in informing regional and national conservation planning efforts.

Identification of geographic linkages among breeding, migratory and wintering common loon Gavia immer populations is needed to inform regional and national conservation planning efforts and compensation of loons lost during marine oil spill events. Satellite telemetry and archival geolocator tags were used to determine the migration patterns and wintering locations of breeding adult and young of the year juvenile common loons captured and marked on lakes in Minnesota, Wisconsin and Michigan. Adult loons typically traveled from breeding lakes, often via larger staging lakes, to the Great Lakes (primarily Lake Michigan) and then on to wintering areas. Most radiomarked juvenile common loons utilized natal lakes or local lakes through mid‐November. Subsequently, the first fall migration of juvenile loons was generally initiated later, and more direct and quicker to wintering areas relative to adults. Among adult (n = 103) and juvenile (n = 23) loons that completed fall migration, most wintered in the Gulf of Mexico (GOM), with smaller proportions wintering off the southern Atlantic Coast or impoundments in the southeastern United States. Spring migration of adults to breeding lakes was less prolonged than fall migration, with adult male loons tending to depart wintering areas earlier than adult females. Juvenile common loons migrated during their first spring from wintering sites in the GOM to summer in the Gulf of St Lawrence/Nova Scotia Coastal region. Juvenile mortality was largely linked to parasitic infection and emaciation; spring appeared to be a survival bottleneck among juvenile loons monitored in our study. Our results identify several areas where common loon conservation efforts could be directed to protect key habitats and minimize stressors during the non‐breeding period.

We measured concentrations of up to 17 polybrominated diphenyl ethers (PBDEs) in plasma of 492 bald eagle (Haliaeetus leucocephalus) nestlings between 1995 and 2017 from 12 study areas in Wisconsin and Minnesota, USA. Geometric mean concentrations of the sum of 9 PBDE congeners (∑PBDE) measured across all years ranged from 2.88 to 10.8 µg/L, and nestlings in urban areas had higher concentrations than those in remote locations. Region-wide from 2006 through 2017, we found that ∑PBDEs declined by 3.8% annually and congeners BDE-47, -99, and -100 declined by 5.6 to 6.5%, whereas BDE-153 and -154 had no significant declines. When categorized by waterbody type, nestlings from Great Lakes and river study areas had higher concentrations of ∑PBDEs than those at inland lakes, but river study areas spanned the extremes. From 2006 to 2017, ∑PBDEs declined by 7.3% annually in Great Lakes nestlings and by 3.2% in nestlings along rivers, and increased by 32.7% at inland lakes. Using a longer dataset (1995-2015), we found that ∑PBDEs declined in Lake Superior nestlings by 3.3% annually. Our results show that PBDEs declined in bald eagle nestling plasma in most study areas since PBDE production was reduced, but that concentrations remain high near urban centers and that trends differ by congener, study area, and waterbody type. Environ Toxicol Chem 2021;40:1606-1618. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Maternal transfer is a predominant route of methylmercury (MeHg) exposure to offspring. We reviewed and synthesized published and unpublished data on maternal transfer of MeHg in birds. Using paired samples of females’ blood (n = 564) and their eggs (n = 1814) from 26 bird species in 6 taxonomic orders, we conducted a meta-analysis to evaluate whether maternal transfer of MeHg to eggs differed among species and caused differential toxicity risk to embryos. Total mercury (THg) concentrations in eggs increased with maternal blood THg concentrations; however, the proportion of THg transferred from females to their eggs differed among bird taxa and with maternal THg exposure. Specifically, a smaller proportion of maternal THg was transferred to eggs with increasing female THg concentrations. Additionally, the proportion of THg that was transferred to eggs at the same maternal blood THg concentration differed among taxonomic orders, with waterfowl (Anseriformes) transferring up to 382% more THg into their eggs than songbirds (Passeriformes). We provide equations to predict THg concentrations in eggs using female blood THg concentrations, and vice versa, which may help translate toxicity benchmarks across tissues and life stages. Our results indicate that toxicity risk of MeHg can vary among bird taxa due to differences in maternal transfer of MeHg to offspring.

We analyzed concentrations and trends of DDE, total PCBs, and mercury in bald eagle (Haliaeetus leucocephalus) nestlings at six study areas in the upper Midwest, 2006-2015, and long-term trends at two Lake Superior sites, 1989-2015. Eaglet plasma from the Apostle Islands in Lake Superior had the highest concentrations of DDE (geometric mean [GM] = 10.6 mu g/L), and DDE concentrations decreased at 5.8% per year across the region from 2006 to 2015, and at 5.5% per year at Lake Superior sites from 1989 to 2015. Concentrations of the sum of 75 PCB congeners (Sigma PCB75) were highest at Pools 3 and 4 of the Mississippi River (GM = 114.8 mu g/L) and did not decline significantly region-wide (all study areas together) between the years of 2006 and 2011. However, at Lake Superior, Sigma PCB75 declined from 1995 to 2011 along the south shore at 3.6% per year, with a non-significant decline at the Apostle Islands. Concentrations of mercury in nestling breast feathers were highest at the upper St. Croix River (GM = 6.66 mu g/g wet weight). At Lake Superior study areas, mercury declined at 1.6% per year from 1991 to 2015; however, from 2006 to 2015 we found no significant trend at one of these same study areas and mercury concentrations apparently increased at two study areas. Mean concentrations of contaminants were below levels associated with significant impairment of reproduction at all sites and mean reproductive rates were > 1.4 young per nest. However, increasing concentrations of mercury in some areas, combined with relatively high concentrations at some nests, suggest that continued monitoring of mercury should be a management priority. Published by Elsevier B.V. on behalf of International Association for Great Lakes Research.

Human development on lakeshore habitats has greatly reduced shrub layer coverage along many North American lakes, negatively impacting associated floral and faunal communities. In northern Wisconsin, several restoration projects have been implemented in recent decades to reverse the impacts of development on lakeshore natural communities. However, restoration practitioners are frequently limited to using containerized plant stock purchased at local nurseries, which can be cost-prohibitive. As an alternative, we tested the effectiveness of using dormant bare-root shrubs in restoration projects along five lakeshores in northern Wisconsin. Because bare-root plant stock can only be planted during narrow windows during the late fall and early spring, we examined the efficacy of using bare-root stock that was grown in a gravel medium (“gravel-culture”) and then planted later during the growing season. We monitored individuals from five species of native shrubs in each of three planting treatments over a three-year period and used a repeated measures, mixed-model approach to compare plant growth of both bare-root and gravel culture stock to growth of containerized stock. Logistic regression models were used to compare the survival of shrubs and treatments. Containerized stock exhibited the greatest growth and survival of the stock types examined. The utility of bare-root and gravel-culture stock varied among species, but for most species our results suggest that gravel-culture may be successfully used to extend the planting window.

Common loons (Gavia immer) staging on the Great Lakes during fall migration are at risk to episodic outbreaks of type E botulism. Information on distribution, foraging patterns, and exposure routes of loons are needed for understanding the physical and ecological factors that contribute to avian botulism outbreaks. Aerial surveys were conducted to document the spatiotemporal distribution of common loons on Lake Michigan during falls 2011–2013. In addition, satellite telemetry and archival geolocator tags were used to determine the distribution and foraging patterns of individual common loons while using Lake Michigan during fall migration. Common loon distribution observed during aerial surveys and movements of individual radiomarked and/or geotagged loons suggest a seasonal pattern of use, with early fall use of Green Bay and northern Lake Michigan followed by a shift in distribution to southern Lake Michigan before moving on to wintering areas. Common loons tended to occupy offshore areas of Lake Michigan and, on average, spent the majority of daylight hours foraging. Dive depths were as deep as 60m and dive characteristics suggested that loons were primarily foraging on benthic prey. A recent study concluded that round gobies (Neogobius melanostomus) are an important prey item of common loons and may be involved in transmission of botulinum neurotoxin type E. Loon distribution coincides with the distribution of dreissenid mussel biomass, an important food resource for round gobies. Our observations support speculation that energy transfer to higher trophic levels via gobies may occur in deep-water habitats, along with transfer of botulinum neurotoxin.

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.

Housing development along lakeshores typically results in the loss of native shoreline vegetation, which can negatively impact habitat structure and associated wildlife populations. We evaluated vegetation restoration efforts on 2 lakeshores in Vilas County, WI, and contrasted them with undeveloped reference lakeshores. The primary goal of the restoration activities was to restore native understory vegetation and habitat structure. Initial measurements made at reference lakeshores showed greater visual obstruction density, greater sapling and shrub densities, greater abundance of downed woody material, and higher canopy coverage relative to initial measurements made at developed lakeshore sites. Three years post-restoration we observed significant increases in visual obstruction density and increased shrub and sapling density at restoration sites. While restoration of complex understory habitats is a slow and uncertain process, a non-metric multi-dimensional scaling ordination of wildlife habitat attributes suggested that restoration sites are on a developmental trajectory that should increase their similarity to reference sites with time. Further monitoring and adaptive management will likely be needed to ensure restoration goals are met.

Senescence, increased mortality that occurs among animals of advanced age, impacts behavior and ecology in many avian species. We investigated actuarial, reproductive, and behavioral senescence using capture, marking, and resighting data from a 26‐year study of common loons Gavia immer. Territorial residents of both sexes exhibited high annual survival (0.94) until their mid 20s, at which point survival fell to 0.76 and 0.77 in males and females, respectively. Sexual symmetry in actuarial senescence is somewhat surprising in this species, because males make a substantially greater investment in territory defense and chick‐rearing and because males engage in lethal contests for territory ownership. Survival of displaced breeders (0.80) was lower than that of territorial residents in both young and old individuals. Old males and females also experienced slightly higher annual probability of eviction (0.16 for males; 0.17 for females) than prime‐aged breeders (0.13 for both sexes), indicating senescence in territory defense. Prime‐aged males reclaimed territories at a high rate (0.49), in contrast to females of the same age (0.33). However, old males resettled with success (0.35) similar to old females (0.31), suggesting that males decline in competitive ability as they age. Nonetheless males, but not females, showed an apparent increase in breeding success over the entire lifetime, a possible indication that very old males make a terminal investment in reproductive output at the cost of survival.

Interest in lakeshore habitat restoration has increased concomitant with growing awareness of the importance of these areas for maintaining water quality and for providing terrestrial and aquatic wildlife habitat. Lakeshore restoration efforts are often limited by the high cost of suitable plant material. We compare the effectiveness of containerized and more cost-effective bareroot and innovative gravel-culture planting techniques for 5 conifer species: balsam fir (Abies balsamea (L.) Mill. [Pinaceae]), white spruce (Picea glauca (Moench) Voss [Pinaceae]), red pine (Pinus resinosa Aiton [Pinaceae]), eastern white pine (Pinus strobus L. [Pinaceae]), and northern white cedar (Thuja occidentalis L. [Cupressaceae]). Plantings were monitored for 4 growing seasons (year of planting and 3 subsequent). Annual growth rates for 4 of the 5 species did not differ significantly among planting techniques. The exception was containerized balsam fir, which experienced a greater height growth rate than did bareroot and gravel-culture stock. Survival of gravel-culture stock was greater than that of bareroot stock and similar to that of containerized stock for all of the conifers examined, except for red pine. Red pine gravel-culture stock had the lowest survival of any species or treatment (29%), suggesting that this technique is poorly suited for this species. We conclude that the time frame for bareroot native conifer planting may be extended for most of the species examined through the midsummer months by growing bareroot stock in irrigated gravel medium until lifting and planting. For some species, however, neither bareroot planting technique is likely to equal or exceed the growth and survival of containerized stock in lakeshore restoration.

Lake riparian areas provide wildlife habitat for a wide variety of species. Residential development throughout such lakeshore areas of the United States has increased exponentially in recent decades. Awareness of the vulnerability and importance of lakeshore ecosystems has increased concurrently. Lakeshore habitat restoration projects have been implemented to mitigate some of the negative impacts of human shoreline development, and containerized (CT) trees are frequently one of the highest costs associated with such restoration projects. As an alternative, we tested the effectiveness of using dormant bare-root (BR) trees in restoration projects along two lakeshores in northern Wisconsin, U.S.A. In addition, we experimented using BR stock that was incorporated into gravel medium at a local nursery and planted later in the summer months. We monitored growth and survival of four native tree species in these three planting treatments over a 3-4-year period. CT red maple (Acer rubra), paper birch (Betula paperifera), and northern red oak (Quercus rubra) increased in size significantly faster than BR and/or gravel culture (GC) counterparts, whereas CT showy mountain ash (Sorbus decora) growth rates were similar to those of BR and GC stock. Mortality was generally low, but for those species/planting treatments with higher mortality (paper birch and red oak), CT trees were more likely to survive than BR or GC trees. Our results show that the success of deciduous BR and/or GC tree stock relative to CT trees is species dependent, and for some species, CT trees' higher growth rates and survivorship could offset their higher costs.

The effects of climate change on biodiversity have emerged as a dominant theme in conservation biology, possibly eclipsing concern over habitat loss in recent years. The extent to which this shifting focus has tracked the most eminent threats to biodiversity is not well documented. We investigated the mechanisms driving shifts in the southern range boundary of a forest and snow cover specialist, the snowshoe hare, to explore how its range boundary has responded to shifting rates of climate and land cover change over time. We found that although both forest and snow cover contributed to the historical range boundary, the current duration of snow cover best explains the most recent northward shift, while forest cover has declined in relative importance. In this respect, the southern range boundary of snowshoe hares has mirrored the focus of conservation research; first habitat loss and fragmentation was the stronger environmental constraint, but climate change has now become the main threat. Projections of future range shifts show that climate change, and associated snow cover loss, will continue to be the major driver of this species' range loss into the future.

Range boundaries are a manifestation of species' tolerances to environmental factors, including climate and human disturbance. As such, studying populations persisting along range boundaries can provide important insights into species' sensitivity to environmental change. Because multiple environmental influences may contribute to a range limit, studies focusing on range boundaries can guide management and conservation of these critical populations. To this end, we quantified the environmental factors associated with snowshoe hare (Lepus americanus) occurrence at their southern range limit in Wisconsin. We surveyed 199 locations across a regional southern range boundary of snowshoe hares and analyzed the data within an occupancy modeling framework to test the hypothesis that this range boundary results from an interaction between winter climate and land cover. We found that dense vegetation structure and increasing forest and snow cover duration had positive effects on snowshoe hare occupancy along their southern range boundary, supporting our prediction that a suite of abiotic factors is associated with the southerly distribution of this winter-adapted mammal. These effects were additive and we found limited support for climate-land cover interactions, forest composition, winter snow depth, or predator occurrence. Spatial predictions of occupancy using only forest and snow cover variables denote a sharp range boundary, further illustrating the importance of these variables in shaping this species distribution. Our results highlight an important vulnerability of snowshoe hares to future climate change, and options for mediating this vulnerability through the maintenance of early successional habitat and forested landscapes along their southern range boundary. (C) 2016 The Wildlife Society.

A field study was conducted in Wisconsin (USA) to characterize in ovo mercury (Hg) exposure in common loons (Gavia immer). Total Hg mass fractions ranged from 0.17 mu g/g to 1.23 mu g/g wet weight in eggs collected from nests on lakes representing a wide range of pH (5.0-8.1) and were modeled as a function of maternal loon Hg exposure and egg laying order. Blood total Hg mass fractions in a sample of loon chicks ranged from 0.84 mu g/g to 3.86 mu g/g wet weight at hatch. Factors other than mercury exposure that may have persistent consequences on development of chicks from eggs collected on low-pH lakes (i.e., egg selenium, calcium, and fatty acid mass fractions) do not seem to be contributing to reported differences in loon chick quality as a function of lake pH. However, it was observed that adult male loons holding territories on neutral-pH lakes were larger on average than those occupying territories on low-pH lakes. Differences in adult body size of common loons holding territories on neutral-versus low-pH lakes may have genetic implications for differences in lake-source-related quality (i.e., size) in chicks. The tendency for high in ovo Hg exposure and smaller adult male size to co-occur in low-pH lakes complicates the interpretation of the relative contributions of each to resulting chick quality. Environ Toxicol Chem 2015;34:1870-1880. (c) 2015 SETAC

We report on patterns and trends in polybrominated diphenyl ethers (PBDEs) in the plasma of 284 bald eagle nestlings sampled between 1995 and 2011 at six study areas in the upper Midwestern United States. Geometric mean concentrations of total PBDEs (Σ of nine congeners) ranged from 1.78 ng/mL in the upper St. Croix River watershed to 12.0 ng/mL on the Mississippi River. Lake Superior nestlings fell between these two extremes. Between 2006 and 2011, trends differed among study areas with three declining, two remaining stable, and one increasing. Variation in ΣPBDE trends among study areas was linked to trends in individual congeners. The lower brominated PBDEs (BDE-47, -99, and -100) declined 4-10% while the higher brominated congeners (BDE-153 and -154) increased by about 7.0% annually from 2006 to 2011. This increase was the greatest in nestlings from the St. Croix River and below its confluence with the Mississippi River. Region-wide, our data suggest ΣPBDEs increased in bald eagle nestlings from 1995 through the mid-2000s and then declined by 5.5% annually from 2006 to 2011. These regional trends are consistent with the removal of penta- and octa-PBDEs from the global market.

The study of habitat selection has long been influenced by the ideal free model, which maintains that young adults settle in habitat according to its inherent quality and the density of conspecifics within it. The model has gained support in recent years from the finding that conspecifics produce cues inadvertently that help prebreeders locate good habitat. Yet abundant evidence shows that animals often fail to occupy habitats that ecologists have identified as those of highest quality, leading to the conclusion that young animals settle on breeding spaces by means not widely understood. Here, we report that a phenomenon virtually unknown in nature, natal habitat preference induction (NHPI), is a strong predictor of territory settlement in both male and female common loons ( Gavia immer ). NHPI causes young animals to settle on natal-like breeding spaces, but not necessarily those that maximize reproductive success. If widespread, NHPI might explain apparently maladaptive habitat settlement.

Residential development has been associated with habitat fragmentation and loss and declining diversity of indigenous species, especially when development occurs in ecologically sensitive environments such as wetlands and/or riparian zones. In recent decades, the upper mid-west region of the United States has experienced a dramatic increase in residential development along lakeshores. In northern Wisconsin, recent studies have documented negative effects of such development on local flora and certain fauna (avian and amphibian communities) but less is known about how mammal communities, especially carnivores, respond to housing development. To quantify the influence of lakeshore development on these taxa, we conducted snow track surveys on 10 pairs of low- and high-development lakes and deployed remote cameras at four lakes in Vilas County, Wisconsin, in 2008. Our results suggest that a higher diversity of carnivores (P = 0.006) were present on low-development lakes. Coyotes (Canis latrans) were detected most frequently (n = 34) especially on low-development lakes. Fishers (Mantes pennant), wolves (Canis lupus), bobcats (Lynx rufus), and northern river otters (Lontra canadensis) were exclusively detected on low-development lakes by snow track surveys. Raccoon (Procyon Iotor) and red fox (Vulpus vulpus) detection was greater on higher-development lakes than low-development lakes. These results also were supported by 12 remote cameras on a subset of four lakes. We also investigated the influence of housing and road density in the surrounding landscape (500 m buffer) on carnivore community composition by means of a non-metric multidimensional scaling ordination. Significant associations were observed between community composition and landscape attributes associated with development. Our results suggest that residential development along lakeshores is having a negative impact on carnivore diversity in this region.