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Arctic ecosystems are undergoing rapid changes, including increasing disturbance by herbivore populations, which can affect plant species coexistence and community assemblages. Although the significance of mosses in Arctic wetlands is well recognized, the long‐term influence of medium‐sized herbivores on the composition of moss communities has received limited attention. We used data from a long‐term (25 years) Greater Snow Goose (Anser caerulescens atlanticus) exclusion experiment in Arctic tundra wetlands to assess changes in the composition of moss communities at multiple spatial scales (cell, 4 cm2; quadrat, 100 cm2; exclosure, 16 m2). We investigated how snow goose grazing and grubbing can alter the composition of the moss community by measuring changes in alpha and beta diversity, as well as in the strength of plant interspecific interactions between moss species. Our results indicate that goose foraging significantly increased species diversity (richness, evenness, and inverse Simpson index) of moss communities at the cell and quadrat scales but not the exclosure scale. Goose foraging reduced the dissimilarity (beta diversity) of moss communities at all three scales, mainly due to decreased species turnover. Furthermore, goose foraging increased positive interaction between moss species pairs. These findings emphasize the critical role of geese in promoting moss species coexistence and increasing homogeneity in Arctic wetlands. This study illustrates how top‐down regulation by herbivores can alter plant communities in Arctic wetlands and highlights the importance of considering herbivores when examining the response of Arctic plant biodiversity to future climate change. [ABSTRACT FROM AUTHOR]

Arctic ecosystems are undergoing rapid changes, including increasing disturbance by herbivore populations, which can affect plant species coexistence and community assemblages. Although the significance of mosses in Arctic wetlands is well recognized, the long‐term influence of medium‐sized herbivores on the composition of moss communities has received limited attention. We used data from a long‐term (25 years) Greater Snow Goose (Anser caerulescens atlanticus) exclusion experiment in Arctic tundra wetlands to assess changes in the composition of moss communities at multiple spatial scales (cell, 4 cm2; quadrat, 100 cm2; exclosure, 16 m2). We investigated how snow goose grazing and grubbing can alter the composition of the moss community by measuring changes in alpha and beta diversity, as well as in the strength of plant interspecific interactions between moss species. Our results indicate that goose foraging significantly increased species diversity (richness, evenness, and inverse Simpson index) of moss communities at the cell and quadrat scales but not the exclosure scale. Goose foraging reduced the dissimilarity (beta diversity) of moss communities at all three scales, mainly due to decreased species turnover. Furthermore, goose foraging increased positive interaction between moss species pairs. These findings emphasize the critical role of geese in promoting moss species coexistence and increasing homogeneity in Arctic wetlands. This study illustrates how top‐down regulation by herbivores can alter plant communities in Arctic wetlands and highlights the importance of considering herbivores when examining the response of Arctic plant biodiversity to future climate change. [ABSTRACT FROM AUTHOR]

Reports of fading vole and lemming population cycles and persisting low populations in some parts of the Arctic have raised concerns about the spread of these fundamental changes to tundra food web dynamics. By compiling 24 unique time series of lemming population fluctuations across the circumpolar region, we show that virtually all populations displayed alternating periods of cyclic/non-cyclic fluctuations over the past four decades. Cyclic patterns were detected 55% of the time (n = 649 years pooled across sites) with a median periodicity of 3.7 years, and non-cyclic periods were not more frequent in recent years. Overall, there was an indication for a negative effect of warm spells occurring during the snow onset period of the preceding year on lemming abundance. However, winter duration or early winter climatic conditions did not differ on average between cyclic and non-cyclic periods. Analysis of the time series shows that there is presently no Arctic-wide collapse of lemming cycles, even though cycles have been sporadic at most sites during the last decades. Although non-stationary dynamics appears a common feature of lemming populations also in the past, continued warming in early winter may decrease the frequency of periodic irruptions with negative consequences for tundra ecosystems. [ABSTRACT FROM AUTHOR]

Reproduction of long-distance migrants can be affected by local conditions on the breeding grounds as well as those encountered during the nonbreeding season through carry-over effects. We show that this is true in Long-tailed Jaegers (Stercorarius longicaudus) because individuals that spent less time flying at sea during winter had a high breeding propensity and a reduced pre-laying interval, but breeding propensity and nesting success were also positively associated with food abundance at the breeding site. This seabird switches from a marine to a terrestrial lifestyle to breed in summer in the Arctic, where it primarily feeds on lemmings. We monitored jaeger reproduction and lemming densities on Bylot Island in the Canadian Arctic for 16 years, and we used geolocator to study annual movements. We assessed whether movement parameters (travel distance, migration duration, phenology, and number of flying bouts inferred by saltwater immersions) during the nonbreeding season affected the breeding propensity, phenology, and success of individuals. We also examined whether cyclic lemming fluctuations influenced Long-tailed Jaeger reproduction and whether nesting success affected the phenology of their outbound migration. We found that increased time spent flying during winter and early arrival at the breeding site reduced breeding propensity. Moreover, spending less time flying during winter shortened the pre-laying period, and advancing laying date increased nesting success. Birds may thus face a trade-off to minimize the relative costs associated with arriving too early and breeding too late. Local food availability had a strong effect on reproduction because breeding propensity and nesting success increased sharply with lemming abundance. Failed breeders advanced their outbound migration by 10 days on average compared to successful ones, but migration duration was similar. Therefore, the unpredictability of the highly seasonal Arctic environment, especially fluctuating food abundance, appears to be a strong driver of reproduction that can modulate the strength of carry-over effects. [ABSTRACT FROM AUTHOR]

During the cold arctic winter, small mammals like lemmings seek refuge inside the snowpack to keep warm and they dig tunnels in the basal snow layer, usually formed of a soft depth hoar, to find vegetation on which they feed. The snowpack, however, is a heterogenous medium and lemmings should use habitats where snow properties favor their survival and winter reproduction. We determined the impact of snow physical properties on lemming habitat use and reproduction in winter by sampling their winter nests for 13 years and snow properties for 6 years across 4 different habitats (mesic, riparian, shrubland, and wetland) on Bylot Island in the Canadian High Arctic. We found that lemmings use riparian habitat most intensively because snow accumulates more rapidly, the snowpack is the deepest and temperature of the basal snow layer is the highest in this habitat. However, in the deepest snowpacks, the basal depth hoar layer was denser and less developed than in habitats with shallower snowpacks, and those conditions were negatively related to lemming reproduction in winter. Shrubland appeared a habitat of moderate quality for lemmings as it favored a soft basal snow layer and a deep snowpack compared with mesic and wetland, but snow conditions in this habitat critically depend on weather conditions at the beginning of the winter. With climate change, a hardening of the basal layer of the snowpack and a delay in snow accumulation are expected, which could negatively affect the winter habitat of lemmings and be detrimental to their populations. [ABSTRACT FROM AUTHOR]

Nonadditive effects from multiple interacting stressors can have unpredictable outcomes on wildlife. Stressors that initially have negligible impacts may become significant if they act in synergy with novel stressors. Wildlife markers can be a source of physiological stress for animals and are ubiquitous in ecological studies. Their potential impacts on vital rates may vary over time, particularly when changing environments impose new stressors.In this study, we evaluated the temporal changes in the combined impact of two stressors, one constant (collar marking) and another one variable over time (hunting intensity), in greater snow geese (Anser caerulescens atlantica). Over a 30‐year period (1990–2019), hunting regulations were liberalized twice, in 1999 and 2009, with the instauration of special spring and winter hunting seasons respectively. We evaluated the effect of collars on goose survival through this period of changing hunting regulations. We compared annual survival of >20,000 adult females marked with and without neck collars using multi‐event capture–recapture models, and partitioned hunting from nonhunting mortality.Survival of geese marked with or without collars was similar in 1990–1998, before hunting regulations were liberalized (average survival [95% CI]: 0.87 [0.86, 0.89]). However, absolute survival of collared geese was 0.05 [0.03, 0.07] lower than that of noncollared geese between 1999 and 2009, and 0.12 [0.09, 0.15] lower after hunting regulations were liberalized further in 2009. Hunting and nonhunting mortality probabilities were both higher in collared birds compared to those without collars.The interaction between the effects of collars and hunting was synergistic because collars affected survival only after the hunting pressure increased significantly. These cumulated stresses probably reduced goose body condition sufficiently to increase their vulnerability to multiple sources of mortality. [ABSTRACT FROM AUTHOR]

Theoretical modeling predicts that both direct and delayed density‐dependence are key factors to generate population cycles. Deciphering density‐dependent processes that lead to variable population growth characterizing different phases of the cycles remains challenging. This is particularly the case for the period of prolonged low densities, which is inherently data deficient. However, demographic analyses based on long‐term capture–mark–recapture datasets can help resolve this question. We relied on a 16‐year (2004–2019) live‐trapping program to analyze the summer demography and movements of a cyclic brown lemming population in the Canadian Arctic. More specifically, we examined if inversely density‐dependent processes could explain why population growth can remain low during the prolonged low phase. We found that the proportion of females in the population was inversely density‐dependent with a strong male‐biased sex ratio at low densities but not at high densities. However, survival of adult females was higher than adult males, but both had lower survival at low densities than at high ones. Distances moved by both adult males and females were density‐dependent, and proportion of females in reproductive condition was weakly density‐dependent as it tended to increase at low density. Individual body condition, measured as monthly change in body mass, was not density‐dependent. Overall, the strong male‐biased sex ratio at very low densities suggests a loss of reproductive potential due to the rarity of females and appears to be the most susceptible demographic factor that could contribute to the prolonged low phase in cyclic brown lemmings. What leads to this sex‐bias in the first place is still unclear, potentially owing to our trapping period limited to the summer, but we suggest that it could be due to high predation rate on breeding females in winter. [ABSTRACT FROM AUTHOR]

Coupling isotope values of feathers and satellite tracking of individuals have the potential to reveal multi-season linkages between wintering habitat, diet and carry-over effects on reproductive parameters in migrating birds. Snowy owls Bubo scandiacus have multiple wintering tactics as they can use both terrestrial and marine resources during the non-breeding season, but their nomadic behaviour complicates their study. We assessed if inter-individual variability in the diet inferred by feather isotopes could be explained by habitat use in winter as determined by satellite telemetry and examined possible carry-over effects on reproduction. Seventeen breeding female snowy owls were equipped with satellite transmitters and sampled for stable isotopes (δ13C and δ15N) in feathers. We found a positive relationship between the use of the coastal and marine environments in winter and the contribution of marine resources to the diet of snowy owls in the previous year based on feather analysis. The proportion of marine contribution to the winter diet was variable among individuals and showed a weak negative relationship to summer body mass but not with laying date or clutch size. Our integrated approach shows the usefulness of isotope analyses to infer habitat use and expand the temporal coverage of radio-tracking studies. [ABSTRACT FROM AUTHOR]

Many avian migrants have not adjusted breeding phenology to climate warming resulting in negative consequences for their offspring. We studied seasonal changes in reproductive success of the greater snow goose (Anser caerulescens atlantica), a long-distance migrant. As the climate warms and plant phenology advances, the mismatch between the timing of gosling hatch and peak nutritive quality of plants will increase. We predicted that optimal laying date yielding highest reproductive success occurred earlier over time and that the seasonal decline in reproductive success increased. Over 25 years, reproductive success of early breeders increased by 42%, producing a steeper seasonal decline in reproductive success. The difference between the laying date producing highest reproductive success and the median laying date of the population increased, which suggests an increase in the selection pressure for that trait. Observed clutch size was lower than clutch size yielding the highest reproductive success for most laying dates. However, at the individual level, clutch size could still be optimal if the additional time required to acquire nutrients to lay extra eggs is compensated by a reduction in reproductive success due to a delayed laying date. Nonetheless, breeding phenology may not respond sufficiently to meet future environmental changes induced by warming temperatures. [ABSTRACT FROM AUTHOR]

Interspecific competition can play a key role in structuring ecological communities. The Arctic tundra is a low productivity ecosystem supporting simple food webs, but several predators often feed on the same prey species, lemmings, known for their large‐amplitude population fluctuations.We examined mechanisms involved in reducing intra‐guild competition and allowing coexistence of four avian predators (snowy owls, glaucous gulls, rough‐legged hawks and long‐tailed jaegers) feeding on a pulsed resource (brown and collared lemmings). We compared the size and species of prey consumed by predators to see if resource partitioning occurred. We also verified if spatial segregation in nesting areas could be another mechanism allowing coexistence. Finally, we tested if the absence of the snowy owl, a dominant and irruptive species, triggered a competitive release on the smallest predator, the jaeger, with respect to prey size and nesting area used.We monitored the breeding of predators and lemming abundance over a 14‐year period on Bylot Island, Canada. We mapped their nesting sites and collected regurgitation pellets to recover lemming mandibles, which were used to infer prey species and size.The size of lemmings consumed varied among species with the largest predators consuming the largest lemmings and the smallest predators consuming the smallest lemmings. All predators consumed more collared than brown lemmings compared to their availability although owls and jaegers consumed relatively more brown lemmings compared to gulls and hawks. Jaegers consumed larger lemmings in the absence of owls than in their presence, suggestive of a short‐term competitive release. We found moderate to low overlap in nesting areas among predators and no evidence of their expansion in the absence of owls, suggesting that spatial distribution is caused by species‐specific habitat preferences.The main mechanism to partition food resources among these avian predators is spatial segregation, and secondarily prey size and species. However, we found evidence that food competition is still present and leads to a niche shift in the smallest predator of the guild. Interspecific competition may thus be a pervasive force in simple, low productivity food webs characterized by pulsed resources. [ABSTRACT FROM AUTHOR]

As top or mesopredators, carnivores play a key role in food webs. Their survival and reproduction are usually thought to be influenced by prey availability. However, simultaneous monitoring of prey and predators is difficult, making it challenging to evaluate the impacts of prey on carnivores' demography. Using 13 years of field data on arctic foxes Vulpes lagopus in the Canadian High Arctic and a capture–recapture multi-event statistical approach, we investigated the hypothesis that increases in lemming abundance (a cyclic and unpredictable food source) and goose colony proximity (a stable but spatially and temporally limited food source) would be associated with increased apparent survival and reproduction probabilities of adults. Adult apparent survival varied greatly across years (0.13–1.00) but was neither affected by lemming nor goose variations in abundance. However, reproduction probabilities were strongly influenced by both lemming abundance and access to the goose colony. A fox breeding in the best conditions of food availability (year of high lemming density inside the goose colony) had a reproduction probability four times higher than one experiencing the worst conditions (year of low lemming density outside the goose colony). Breeding status of individuals also played a role, with breeders having a 10–20% higher probability of survival and 30% higher probability of reproduction the following year than non-breeders. As the Arctic ecosystem changes due to increased temperatures and species ranges, this study will allow better predictions of predator responses to management or environmental changes and a better understanding of ecosystem functioning. [ABSTRACT FROM AUTHOR]

The presence of a snowpack, which may last up to 9 months in the Arctic, can provide insulation from the cold winter temperature for small mammals living beneath it, such as lemmings. Since lemmings have to move through the snowpack during that period, it is important to better understand how the physical properties of snow affect the way they dig tunnels. Here, we tested 1) whether lemmings systematically dig in the snowpack at the ground level where they can find their food plants, and 2) whether they choose the softest snow layer in which to dig, which is usually the depth hoar layer in the arctic snowpack. We found 33 lemming tunnels in 2017 and 2018 by digging through the snow at the sites of arctic fox attacks on lemmings. Contrary to our expectation, almost all the tunnels (32/33) were found to be higher than ground level, probably because of the presence of obstacles (i.e. melt-freeze crusts or hummocks) at the base of the snowpack. As predicted, all tunnels were dug in the soft depth hoar layer, which had a lower density than snow layers below and above it. Lemmings also showed a preference to dig their tunnels at the top of the depth hoar, just below a hard snow layer. Systematically digging their tunnels in the lowest-density snow layer, regardless of its height in the snow pack, could be a strategy for lemmings to minimize energy expenditure, which could improve their survival and chances of reproducing in winter. [ABSTRACT FROM AUTHOR]

Ilmenite-rich black sands from an alluvial deposit of Barbacoas (Nariño, Colombia) were used as a natural source aiming to obtain a low-cost and highly available photocatalyst. Mineral concentrates were obtained by gravimetric concentration in a Wilfley table (deck tilt angle: 11–14°) followed by dry magnetic or wet electromagnetic separation. Afterwards, the particle size was manually reduced down to −325 mesh. Rietveld refinements using X-ray diffraction data showed that the highest purity achieved was 93.46% of ilmenite (FeTiO3). Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy revealed a polyhedral morphology with an average grain size of 1.33–2.27 μm, granular inclusions of aluminosilicates and appreciable quantities of manganese. The band-gap values determined by UV-Vis diffuse reflectance spectroscopy were underestimated compared to those reported in the literature, given the impurities in the samples and their optical behavior. Photoluminescence experiments provided a band-gap of 2.68 eV. The photo-oxidative and photo-reductive capabilities of the concentrates were evaluated in the degradation of methyl orange in aqueous solution under UV irradiation. 99% of discoloration was achieved after 50 min for oxidation and after 20 min for reduction, showing the potential of ilmenite-rich concentrates as photocatalysts. [ABSTRACT FROM AUTHOR]

Non-consumptive effects of predation have rarely been assessed in wildlife populations even though their impact could be as important as lethal effects. Reproduction of individuals is one of the most important demographic parameters that could be affected by predator-induced stress, which in turn can have important consequences on population dynamics. We studied non-consumptive effects of predation on the reproductive activity (i.e., mating and fertilization) of a cyclic population of brown lemmings exposed to intense summer predation in the Canadian High Arctic. Lemmings were live-trapped, their reproductive activity (i.e., testes visible in males, pregnancy/lactation in females) assessed, and predators were monitored during the summers of 2014 and 2015 within a 9 ha predator-reduction exclosure delimited by a fence and covered by a net, and on an 11 ha control area. Stress levels were quantified non-invasively with fecal corticosterone metabolites (FCM). We found that FCM levels of lemmings captured outside the predator exclosure (n = 50) were 1.6 times higher than inside (n = 51). The proportion of pregnant/lactating adult females did not differ between the two areas, nor did the proportion of adult scrotal males. We found that lemmings showed physiological stress reactions due to high predation risk, but had no sign of reduced mating activity or fertility. Thus, our results do not support the hypothesis of reproductive suppression by predator-induced stress. [ABSTRACT FROM AUTHOR]

Migratory species can exploit many habitats over vast geographic areas and adopt various patterns of space and habitat use throughout their annual cycle. In nomadic species, determinants of habitat use during the non‐breeding season are poorly known due to the unpredictability of their movement patterns. Here, we analysed variability in wintering space and habitat use by a highly nomadic species, the snowy owl, in eastern North America. Using 21 females tracked by satellite telemetry between 2007 and 2016, we 1) assessed how space use patterns in winter varied according to the type of environment (marine vs terrestrial), latitudinal zone (Arctic vs temperate), local snow conditions and lemming densities and 2) investigated winter habitat and site fidelity. Our results confirmed a high inter‐individual variation in patterns of habitat use by wintering snowy owls. Highly‐used areas were concentrated in the Arctic and in the marine and coastal environments. Owls wintering in the marine environment travelled over longer distances during the winter, had larger home ranges and these were divided in more smaller zones than individuals in terrestrial environments. Wintering home range sizes decreased with high winter lemming densities, use of the marine environment increased following high summer lemming densities, and a thick snow cover in autumn led to later settlement on the wintering ground. Contrary to expectations, snowy owls tended to make greater use of the marine environment when snow cover was thin. Snowy owls were highly consistent in their use of a given wintering environment and a specific latitudinal zone between years, but demonstrated flexibility in their space use and a modest site fidelity. The snowy owls’ consistency in wintering habitat use may provide them with advantages in terms of experience but their mobility and flexibility may help them to cope with changing environmental conditions at fine spatial scale. [ABSTRACT FROM AUTHOR]

The snowy owl is an elusive arctic predator known for its nomadic behaviour. Satellite tracking has revealed that some adult snowy owls could make an extensive use of the marine environment during the non-breeding season. However, the relative contribution of marine resources to their diet is unknown. Stable isotope analyses can be useful to document the diet of mobile animals during periods of the year when individuals are less accessible. This study aimed to assess variation in isotopic values (δ13C and δ15N) of various feather types, and the usefulness of feathers to determine the contribution of the marine environment to the winter diet of snowy owls captured in summer. We sampled feathers coming from 6 body regions of 18 breeding females at two sites in the eastern Canadian Arctic in 2013 and 2014. Prior to analyses, diet-tissue discrimination factors of snowy owl feathers were established in captivity. Variability in isotopic values among feather types was relatively low and pairwise correlations in isotopic values between feathers on the same individual were variable and often low, which suggests differences in the diet at the time when various feathers were synthesized. Diet reconstruction models detected a contribution of marine sources to snowy owl feathers ranging from 4 to 19% among feather types. However, the marine contribution was highly variable when single feathers were examined within individuals, ranging from 3 to 71%. This indicated that no single feather type could be used alone to reliably infer the contribution of marine resources to the winter diet of owls, possibly due to a high variability in the timing and sequence of molt. For asynchronous molters like snowy owls, we recommend sampling multiple feathers from various body regions, excluding wing feathers, to investigate winter diet or habitat use. [ABSTRACT FROM AUTHOR]

Interest in the ecology of stress in wild populations has triggered the development of noninvasive methods for quantifying stress hormones. Measurement of fecal corticosteroid metabolites (FCMs) is one such method, but it is still unclear whether FCMs can be a reliable proxy of free plasma glucocorticoids. To assess the validity of this assumption, we carried out a robust assessment on brown lemmings (Lemmus trimucronatus) from Bylot Island, Nunavut, Canada, that were hand captured and anesthetized and related plasma glucocorticoid levels to fecal metabolite glucocorticoid levels. We examined endogenous factors that could explain interindividual variability. Blood corticosterone was measured from samples obtained on capture and 30 min later, and FCM levels were measured from animals kept in captivity for 72 h. Plasma free corticosterone increased 135-fold over baseline values 30 min after capture, which confirmed that initial handling was perceived as a stressor. We found that FCM levels were highly related with free (marginal Rm2 = 0.53) but not with total (Rm2 = 0.02) corticosterone levels, regardless of age, sex, and reproductive condition. FCM levels started increasing 2 h after capture and reached maximum levels 4 h after capture. No circadian rhythm in FCMs was found. Plasma total corticosterone levels were much higher in adult females compared with adult males, but this difference was much smaller when measuring free corticosterone levels and FCM levels. Our results suggest that FCM levels are good measures of stress by being closely related to plasma free corticosterone levels in brown lemmings. [ABSTRACT FROM AUTHOR]

Between the early 1900s and the 1990s, the greater snow goose Anser caerulescens atlanticus population grew from 3000 individuals to more than 700 000. Because of concerns about Arctic degradation of natural habitats through overgrazing, a working group recommended the stabilization of the population. Declared overabundant in 1998, special management actions were then implemented in Canada and the United States. Meanwhile, a cost-benefit socioeconomic analysis was performed to set a target population size. Discussions aiming towards attaining a common vision were undertaken with stakeholders at multiple levels. The implemented measures have had varying success; but population size has been generally stable since 1999. To be effective and meet social acceptance, management actions must have a scientific basis, result from a consensus among stakeholders, and include an efficient monitoring programme. In this paper, historical changes in population size and management decisions along with past and current challenges encountered are discussed. [ABSTRACT FROM AUTHOR]

Aging individuals is a prerequisite to many studies in wildlife biology. In mammals, the most accurate methods are based on cement lines analysis and require tooth extraction. Here, we adapted a method based on tooth wear assessment in live individuals and calibrated against cement lines counts on dead individuals. We developed and tested this less invasive method in arctic foxes Vulpes lagopus. We photographed dentition of live individuals captured in 2006–2013 and of skulls collected opportunistically in 2003–2013. Five observers assessed twice the tooth wear of 245 sets of pictures (left, frontal, and right views of the dentition for 179 captures and 66 skulls, with a mean of 7.2 pictures per set) to obtain a teeth condition index (TCI) for each set. TCI was highly repeatable, with an intraclass correlation coefficient averaging 0.89 and 0.83 within and between observers, respectively. We then used 44 known‐aged individuals to predict fox age from TCI through linear regression (age = 0.62 × TCI + 1.04, r2 = 0.64). We tested through jackknife validation the ability of this model to accurately age foxes. The rate of correct classification of exact age was 39%, while 80% and 100% of predicted ages were within one and two years of the true age, respectively. The model predicted correctly the age class (young, prime‐age adult, old) of individuals 75% of the time. We conclude that our proposed method, which is much less invasive than those based on tooth extraction, can allow progress in the study of demography of arctic foxes, and potentially other mammal species. [ABSTRACT FROM AUTHOR]

The science of complex systems is increasingly asked to forecast the consequences of climate change. As a result, scientists are now engaged in making predictions about an uncertain future, which entails the efficient communication of this uncertainty. Here we show the benefits of hierarchically decomposing the uncertainty in predicted changes in animal population size into its components due to structural uncertainty in climate scenarios (greenhouse gas emissions and global circulation models), structural uncertainty in the demographic model, climatic stochasticity, environmental stochasticity unexplained by climate-demographic trait relationships, and sampling variance in demographic parameter estimates. We quantify components of uncertainty surrounding the future abundance of a migratory bird, the greater snow goose (Chen caeruslescens atlantica), using a process-based demographic model covering their full annual cycle. Our model predicts a slow population increase but with a large prediction uncertainty. As expected from theoretical variance decomposition rules, the contribution of sampling variance to prediction uncertainty rapidly overcomes that of process variance and dominates. Among the sources ofprocess variance, uncertainty in the climate scenarios contributed less than 3% of the total prediction variance over a 40-year period, much less than environmental stochasticity. Our study exemplifies opportunities to improve the forecasting of complex systems using long-term studies and the challenges inherent to predicting the future of stochastic systems. [ABSTRACT FROM AUTHOR]

It is generally recognized that delayed density-dependence is responsible for cyclic population dynamics. However, it is still uncertain whether a single factor can explain why some rodent populations fluctuate according to a 3-4 yr periodicity. There is increasing evidence that predation may play a role in lemming population cycles, although this effect may vary seasonally. To address this issue, we conducted an experiment where we built a large exclosure (9 ha) to protect brown lemmings ( Lemmus trimucronatus) from avian and terrestrial predators. We tested the hypothesis that predation is a limiting factor for lemmings by measuring the demographic consequences of a predator reduction during the growth and peak phases of the cycle. We assessed summer (capture-mark-recapture methods) and winter (winter nest sampling) lemming demography on two grids located on Bylot Island, Nunavut, Canada from 2008 to 2015. The predator exclosure became fully effective in July 2013, allowing us to compare demography between the control and experimental grids before and during the treatment. Lemming abundance, survival and proportion of juveniles were similar between the two grids before the treatment. During the predator-reduction period, summer densities were on average 1.9× higher inside the experimental grid than the control and this effect was greatest for adult females and juveniles (densities 2.4× and 3.4× higher, respectively). Summer survival was 1.6× higher on the experimental grid than the control whereas body mass and proportion of juveniles were also slightly higher. Winter nest densities remained high inside the predator reduction grid following high summer abundance, but declined on the control grid. These results confirm that predation limits lemming population growth during the summer due to its negative impact on survival. However, it is possible that in winter, predation may interact with other factors affecting reproduction and ultimately population cycles. [ABSTRACT FROM AUTHOR]

Environmental constraints are strong in migratory species that breed in the Arctic. In addition to breeding, Anatidae have to renew all their flight feathers during the short arctic summer. We examine how temporal constraints and climate affect the phenology of flight feather moult in the greater snow goose Chen caerulescens atlantica, a High Arctic nesting species. We used a database of 1412 moulting adult females measured over 15 yr on Bylot Island, Nunavut. Ninth (9th) primary length was used to determine the moult stage and speed of feather growth. We found a positive relationship between median annual hatching and moult initiation dates and the slope did not differ from 1. The interval between hatching and moult initiation was thus rather fixed and geese did not initiate moult earlier when reproductive phenology was delayed. Nonetheless, there was no relationship between median hatching date and the date at which birds regained flight capacity, suggesting that date of end of moult is independent of the reproductive phenology. There was a trend for an increase in the speed of flight feather growth in years with delayed hatching date. This is the most likely mechanism that could explain moult phenology adjustment in this species. Finally, we found a positive relationship between 9th primary length (corrected for inter-annual variations) and body condition, suggesting a delay in moulting for individuals in poor condition. These results suggest that moult plasticity is primarily governed by variations in feather growth speed. This phenotypic plasticity could be necessary to complete flight feather renewal before the end of the arctic summer, independently of reproductive phenology and spring environmental conditions. Our novel results suggest possible phenological adjustments through moult speed, which was considered constant in geese until now. [ABSTRACT FROM AUTHOR]

Tetrahydro-1-benzazepines have been described as potential antiparasitic drugs for the treatment of chagas disease and leishmaniasis, two of the most important so-called `forgotten tropical diseases' affecting South and Central America, caused by Trypanosoma cruzi and Leishmania chagasi parasites, respectively. Continuing our extensive work describing the structural characteristics of some related compounds with interesting biological properties, the crystallographic features of three epoxy-1-benzazepines, namely (2 SR,4 RS)-6,8-dimethyl-2-(naphthalen-1-yl)-2,3,4,5-tetrahydro-1 H-1,4-epoxy-1-benzazepine, (1), (2 SR,4 RS)-6,9-dimethyl-2-(naphthalen-1-yl)-2,3,4,5-tetrahydro-1 H-1,4-epoxy-1-benzazepine, (2), and (2 SR,4 RS)-8,9-dimethyl-2-(naphthalen-1-yl)-2,3,4,5-tetrahydro-1 H-1,4-epoxy-1-benzazepine, (3), all C22H21NO, and two 1-benzazepin-4-ols, namely 7-fluoro- cis-2-[( E)-styryl]-2,3,4,5-tetrahydro-1 H-1-benzazepin-4-ol, C18H18FNO, (4), and 7-fluoro- cis-2-[( E)-pent-1-enyl]-2,3,4,5-tetrahydro-1 H-1-benzazepin-4-ol, C15H20FNO, (5), are described. Some peculiarities in the crystallization behaviour were found, involving significant variations in the crystalline structures as a result of modest changes in the peripheral substituents in (1)-(3) and the occurrence of discrete disorder due to the molecular overlay of enantiomers with more than one conformation in (5). In particular, an interesting phase change on cooling was observed for compound (5), accompanied by an approximate fourfold increase of the unit-cell volume and a change of the Z′ value from 1 to 4. This transition is a consequence of the partial ordering of the pentenyl chains in half of the molecules breaking half of the symmetry axes observed in the room-temperature structure of (5). The structural assembly in all the title compounds is characterized by not only (N,O)-H...(O,N) hydrogen bonds, but also by unconventional C-H...O contacts, resulting in a wide diversity of packing. [ABSTRACT FROM AUTHOR]

In highly seasonal environments, timing of breeding of organisms is typically set to coincide with the period of highest resource availability. However, breeding phenology may not change at a rate sufficient to keep up with rapid changes in the environment in the wake of climate change. The lack of synchrony between the phenology of consumers and that of their resources can lead to a phenomenon called trophic mismatch, which may have important consequences on the reproductive success of herbivores. We analyzed long-term data (1991-2010) on climate, plant phenology and the reproduction of a long-distance Arctic migrant, the greater snow goose ( Chen caerulescens atlantica), in order to examine the effects of mismatched reproduction on the growth of young. We found that geese are only partially able to adjust their breeding phenology to compensate for annual changes in the timing of high-quality food plants, leading to mismatches of up to 20 days between the two. The peak of nitrogen concentration in plants, an index of their nutritive quality for goslings, occurred earlier in warm springs with an early snow melt. Likewise, mismatch between hatch dates of young and date of peak nitrogen was more important in years with early snow melt. Gosling body mass and structural size at fledging was reduced when trophic mismatch was high, particularly when the difference between date of peak nitrogen concentration and hatching was >9 days. Our results support the hypothesis that trophic mismatch can negatively affect the fitness of Arctic herbivores and that this is likely to be exacerbated by rising global temperatures. [ABSTRACT FROM AUTHOR]

The causes of cyclical fluctuations in animal populations remain a controversial topic in ecology. Food limitation and predation are two leading hypotheses to explain small mammal population dynamics in northern environments. We documented the seasonal timing of the decline phases and demographic parameters (survival and reproduction) associated with population changes in lemmings, allowing us to evaluate some predictions from these two hypotheses., We studied the demography of brown lemmings ( Lemmus trimucronatus), a species showing 3- to 4-year population cycles in the Canadian Arctic, by combining capture-mark-recapture analysis of summer live-trapping with monitoring of winter nests over a 10-year period. We also examined the effects of some weather variables on survival., We found that population declines after a peak occurred between the summer and winter period and not during the winter. During the summer, population growth was driven by change in survival, but not in fecundity or proportion of juveniles, whereas in winter population growth was driven by changes in late summer and winter reproduction., We did not find evidence for direct density dependence on summer demographic parameters, though our analysis was constrained by the paucity of data during the low phase. Body mass, however, was highest in peak years., Weather effects were detected only in early summer when lemming survival was positively related to snow depth at the onset of melt but negatively related to rainfall., Our results show that high mortality causes population declines of lemmings during summer and fall, which suggests that predation is sufficient to cause population crashes, whereas high winter fecundity is the primary factor leading to population irruptions. The positive association between snow depth and early summer survival may be due to the protective cover offered by snow against predators. It is still unclear why reproduction remains low during the low phase. [ABSTRACT FROM AUTHOR]

This article proposes an epistemological and ontological reflection on Journalism and it's connections to the philosophic concepts of Truth and Reality - which, nowadays, are regarded with constraint as some kind of taboo in the communication field. For this purpose, the reflection is based on John Searle's philosophical though on the realism - both metaphysical (on reality) and alethic (on truth) - in order to propose a Journalistic Realism. In this article, we intend to expose how the acknowledge of Journalism's constructivist nature shouldn't lead to the rejection of the idea of a brute reality or of the search for the truth. We estipulate that the journalistic construction is made of an aprioristic reality and that, as it seeks to report reality, it should seek truth also. [ABSTRACT FROM AUTHOR]

Adaptive management of harvested waterfowl requires accurate estimations of demographic parameters. These must also be representative of the targeted population. In the greater snow goose, all demographic parameters so far have been estimated from long-term banding conducted at a single nesting colony in the Arctic, Bylot Island, where 15% of the population breeds. We used data from a second banding program conducted on Ellesmere Island, 800 km north of Bylot Island and near the northern limit of the breeding range, to compare adult survival between these 2 breeding sites over the period 2007-2011. This allowed us to determine the representativeness of demographic parameters estimated from the Bylot colony. We used a multi-event capture-recapture model combining recaptures, resightings of neckbanded birds, and recoveries on a seasonal basis, which allowed us to test specifically for differences in survival during the migration periods. Despite differences in migration distance (20% longer for Ellesmere Island) and environmental conditions, survival rate of birds from these 2 breeding sites were similar in all seasons. Annual survival ranged from 0.72 to 0.79. This apparent absence of a cost of migration on survival may be explained by the canalization hypothesis: variance in adult survival of the greater snow goose, a long-lived species, caused by environmental factors may have been reduced because of selection pressure on this trait, which is closely linked to fitness. The absence of spatial variation in adult survival suggests that the extrapolation of survival parameters estimated from the Bylot Island colony to the entire population may be valid. © 2015 The Wildlife Society. [ABSTRACT FROM AUTHOR]

The influence of the Mn precursor on the formation of polytypes was studied within the Ba–Ce–Mn–O system. Minor changes in the mean oxidation state of Mn cations guide the reaction route through different pathways to obtain the iso-stoichiometric 12R-Ba4CeMn4O12−δ or 10H-Ba5Ce1.25Mn3.75O15−δ compounds. This behaviour was controlled using MnO2 or MnCO3 as starting chemical precursors. The understanding of such tendencies allowed the synthesis of the new 10H-Ba5Ce0.83Mn4.17O15−δ composition through a two-step reaction route. This compound crystallizes in a hexagonal symmetry with space group P63/mmc (No. 194) and cell parameters a = b = 5.77650(6) Å and c = 23.8590(4) Å. Its main characteristic is the presence of pure [Mn4O15] oligomers, establishing a difference with respect to the already known 10H-Ba5Ce1.25Mn3.75O15 polytype for which the principal feature was a mixed metal occupancy within [Ce0.25Mn3.75O15] tetramers. This difference generates strong antiferromagnetic (AFM) exchanges, contrary to the metamagnetic-like transition observed in 10H-Ba5Ce1.25Mn3.75O15. It is concluded that full Mn occupancy in [Mn3O12] or [Mn4O15] sub-units induces a robust AFM character. [ABSTRACT FROM AUTHOR]

Sympatric species are expected to minimize competition by partitioning resources, especially when these are limited. Herbivores inhabiting the High Arctic in winter are a prime example of a situation where food availability is anticipated to be low, and thus reduced diet overlap is expected. We present here the first assessment of diet overlap of high arctic lemmings during winter based on DNA metabarcoding of feces. In contrast to previous analyses based on microhistology, we found that the diets of both collared (Dicrostonyx groenlandicus) and brown lemmings (Lemmus trimucronatus) on Bylot Island were dominated by Salix while mosses, which were significantly consumed only by the brown lemming, were a relatively minor food item. The most abundant plant taxon, Cassiope tetragona, which alone composes more than 50% of the available plant biomass, was not detected in feces and can thus be considered to be non-food. Most plant taxa that were identified as food items were consumed in proportion to their availability and none were clearly selected for. The resulting high diet overlap, together with a lack of habitat segregation, indicates a high potential for resource competition between the two lemming species. However, Salix is abundant in the winter habitats of lemmings on Bylot Island and the non-Salix portion of the diets differed between the two species. Also, lemming grazing impact on vegetation during winter in the study area is negligible. Hence, it seems likely that the high potential for resource competition predicted between these two species did not translate into actual competition. This illustrates that even in environments with low primary productivity food resources do not necessarily generate strong competition among herbivores. [ABSTRACT FROM AUTHOR]

Understanding how climate change will affect animal population dynamics remains a major challenge, especially in long-distant migrants exposed to different climatic regimes throughout their annual cycle., We evaluated the effect of temperature throughout the annual cycle on demographic parameters (age-specific survival and recruitment, breeding propensity and fecundity) of the greater snow goose ( Chen caerulescens atlantica L.), an arctic-nesting species. As this is a hunted species, we used the theory of exploited populations to estimate hunting mortality separately from natural mortality in order to evaluate climatic effects only on the latter form of mortality., Our analysis was based on a 22-year marking study ( n = 27 150 females) and included live recaptures at the breeding colony and dead recoveries from hunters. We tested the effect of climatic covariates by applying a procedure that accounts for unexplained environmental variation in the demographic parameter to a multistate capture-mark-recapture recruitment model., Breeding propensity, clutch size and hatching probability all increased with high temperatures on the breeding grounds. First-year survival to natural causes of mortality increased when temperature was high at the end of the summer, whereas adult survival was not affected by temperature. On the contrary, accession to reproduction decreased with warmer climatic conditions during the non-breeding season., Survival was strongly negatively related to hunting mortality in adults, as expected, but not in first-year birds, which suggests the possibility of compensation between natural and hunting mortality in the latter group., We show that events occurring both at and away from the breeding ground can affect the demography of migratory birds, either directly or through carryover effects, and sometimes in opposite ways. This highlights the need to account for the whole life cycle of an animal when attempting to project the response of populations to future climatic changes. [ABSTRACT FROM AUTHOR]

Breeding propensity, i.e., the probability that a mature female attempts to breed in a given year, is a critical demographic parameter in long-lived species. Life-history theory predicts that this trait should be affected by reproductive trade-offs so that the probability of future reproduction should depend on the current reproductive investment. However, breeding propensity is one of the most difficult parameters to estimate because nonbreeders are often absent from the breeding area, thereby requiring the inclusion of unobservable states in the analysis. We developed a new methodological approach by integrating a robust design sampling scheme within the multi-event capture-recapture framework. Our new model accounted for uncertainty in state assignation while allowing for departure of individuals between secondary sampling occasions. We applied this model to a long-term data set of female Greater Snow Geese (Chen caerulescens atlantica) to estimate breeding propensity and to investigate potential reproductive costs. We combined resightings during the nesting stage and recapture at the end of the breeding season to estimate breeding propensity and nesting success, and added recoveries to improve survival probability estimates. We found that both breeding propensity and nesting success depended upon breeding status in the previous year, though not survival. Successful breeders had a lower breeding propensity than failed breeders in the following year, but a higher nesting success. Individuals absent from the breeding colony had a low breeding propensity, but a high nesting success the following year. Our results suggest a cost of reproduction on breeding propensity in the next year, but once females decide to breed, nesting success is likely driven by individual quality. An added benefit of our model is that, unlike previous models with unobservable states, all parameters were identifiable when survival and breeding probabilities were fully state dependent. Our new multi-event framework is a flexible tool that can be applied to a large range of species to estimate breeding propensity and to investigate reproductive trade-offs. [ABSTRACT FROM AUTHOR]

In low-productivity environments such as the tundra, it has been proposed that regular, multi-annual population cycles of lemmings could be driven by winter food depletion in years of peak abundance. If lemming population dynamics is controlled by food resources, we predict that (1) winter grazing should negatively impact the abundance of food plants, (2) this impact should be proportional to lemming density and (3) high lemming winter grazing pressure should result in reduced plant growth during the following summer. We tested these predictions on Bylot Island, Nunavut, Canada, where two species of lemmings are present: the brown ( Lemmus trimucronatus) and collared lemming ( Dicrostonyx groenlandicus). We installed 16 exclosures in their preferred wintering habitat (snowbeds) and annually sampled plant biomass inside and outside exclosures at snow melt and at peak growth during the summers of 2009-2012, covering a full population cycle. Winter grazing had no impact on total vascular plant or moss biomass at snow melt in all years. Among plant families, only Caryophyllaceae, which was uncommon, showed a decline. In moss taxa, a negative effect was found on Polytrichum in only 1 year out of three. Overall, plant regrowth during the subsequent summer showed annual variation and tended to be reduced in the 2 years of high lemming abundance. However, this could be a consequence of summer grazing. Overall, the impact of lemming winter grazing on plants was weak and short-lived, even in years of high lemming abundance. Therefore, our results are not consistent with the hypothesis that food depletion during winter was the cause of the lemming decline following peak abundance at our study site. Other factors may limit lemming populations and prevent them from reaching densities high enough to exhaust their food resources. [ABSTRACT FROM AUTHOR]

In many arctic herbivores, the growth of young depends upon a synchrony between hatching date and seasonal change in plant nutritive quality. If plants respond more quickly than herbivores to climate warming, this may cause a mismatch between the availability of high-quality food and the hatching of young. This study examines the impact of experimental warming on the main food plants of an arctic herbivore, the greater snow goose ( Chen caerulescens atlantica L.) breeding on Bylot Island, Nunavut, Canada., During summers 2007-2009, we increased the temperature using small glasshouses (open-top chambers, OTC) in two habitats, wetlands and mesic tundra. Every 10 days, we measured above-ground plant biomass and a proxy of nutritive quality, nitrogen concentration, of graminoid plants in warmed and control plots from snowmelt in June until late July., Open-top chambers increased mean maximum temperature by up to 2.0 °C in wetlands and 4.6 °C in mesic tundra. Annual warming significantly increased biomass of graminoids by up to 29% in wetlands and 20% in mesic tundra. There was no difference in nitrogen concentration of the four plant species sampled ( Dupontia fisheri, Eriophorum scheuchzeri, Arctagrostis latifolia and Luzula spp.) early in the season, but the seasonal decline in nitrogen occurred more rapidly in warmed than in control plots (10% to 14% less nitrogen in warmed plots in July). This effect was consistent across the 3 years of the experiment and independent of annual variation in plant phenology. There was either a weak positive effect or no effect of the warming treatment on the nitrogen biomass of plants depending on species or period of the season., Synthesis. Our results show that warming speeds up plant phenology and the seasonal decline in nutritive quality for arctic herbivores. Because young herbivores like geese are highly sensitive to the nitrogen concentration of their food, a warmer climate will likely reduce their growth. Climate warming may therefore have a negative impact on the population dynamic of arctic herbivores by reducing the quality of their summer forage. [ABSTRACT FROM AUTHOR]

Studies of population dynamics of long-lived species have generally focused on adult survival because population growth should be most sensitive to this parameter. However, actual variations in population size can often be driven by other demographic parameters, such as juvenile survival, when they show high temporal variability. We used capture-recapture data from a long-term study of a hunted, migratory species, the greater snow goose ( Chen caerulescens atlantica), to assess temporal variability in first-year survival and the relative importance of natural and hunting mortality. We also conducted a parasite-removal experiment to determine the effect of internal parasites and body condition on temporal variation in juvenile survival. We found that juvenile survival showed a higher temporal variability than adult survival and that natural mortality was more important than hunting mortality, unlike in adults. Parasite removal increased first-year survival and reduced its annual variability in females only. Body condition at fledging was also positively correlated with first-year survival in treated females. With reduced parasite load, females, which are thought to invest more in their immune system than males according to Bateman's principle, could probably reallocate more energy to growth than males, leading to a higher survival. Treated birds also had a higher survival than control ones during their second year, suggesting a developmental effect that manifested later in life. Our study shows that natural factors such as internal parasites may be a major source of variation in juvenile survival of a long-lived, migratory bird, which has implications for its population dynamics. [ABSTRACT FROM AUTHOR]

Arctic wildlife is often presented as being highly at risk in the face of current climate warming. We use the long-term (up to 24 years) monitoring records available on Bylot Island in the Canadian Arctic to examine temporal trends in population attributes of several terrestrial vertebrates and in primary production. Despite a warming trend (e.g. cumulative annual thawing degree-days increased by 37% and snow-melt date advanced by 4-7 days over a 23-year period), we found little evidence for changes in the phenology, abundance or productivity of several vertebrate species (snow goose, foxes, lemmings, avian predators and one passerine). Only primary production showed a response to warming (annual above-ground biomass of wetland graminoids increased by 123% during this period). We nonetheless found evidence for potential mismatches between herbivores and their food plants in response to warming as snow geese adjusted their laying date by only 3.8 days on average for a change in snow-melt of 10 days, half of the corresponding adjustment shown by the timing of plant growth (7.1 days). We discuss several reasons (duration of time series, large annual variability, amplitude of observed climate change, nonlinear dynamic or constraints imposed by various rate of warming with latitude in migrants) to explain the lack of response by herbivores and predators to climate warming at our study site. We also show how length and intensity of monitoring could affect our ability to detect temporal trends and provide recommendations for future monitoring. [ABSTRACT FROM AUTHOR]

Rising temperatures and changes in the precipitation regime will have a strong impact on the quality of the snow cover in the Arctic. A snow cover of good quality protecting lemmings from cold temperatures and predators is thought to be an important factor for maintaining the cyclic dynamic of their populations in the tundra. We examined if the characteristics of annual fluctuations (amplitude and shape of phases) in brown lemming ( Lemmus trimucronatus) density could be determined by snow depth, snow density, sub-nivean temperature and persistence of snow. Using an 18-year time series of brown lemming abundance on Bylot Island in the Canadian Arctic, we tested if snow variables could explain the residual variation between the observed lemming density and the one predicted by models where cyclicity had been accounted for. Our analysis provides support for the hypothesis that snow cover can affect the amplitude and possibly also the periodicity of lemming population cycles in the High Arctic. Summer abundance of brown lemmings was higher following winters with a deep snow cover and a low-density snow pack near the ground but was unaffected by the date of establishment or melting and duration of the snow cover. Two snow variables showed a temporal trend; mean winter snow depth tended to increase and date of establishment of the hiemal threshold occurred earlier over time. These temporal trends, which should be favourable to lemmings, may explain why healthy population cycles have apparently been maintained at our study site contrary to other Arctic sites. [ABSTRACT FROM AUTHOR]

In the Arctic tundra, snow is believed to protect lemmings from mammalian predators during winter. We hypothesized that snow quality (depth and hardness) should affect mammalian predation rates on lemmings, but that this effect would depend on the predator hunting strategy; and that predation by ermines (Mustela erminea), which can hunt lemmings under the snow, should be higher in preferred lemming habitats. We measured snow depth and hardness at tunnels made by arctic fox (Vulpes lagopus) predation attempts, at winter nests nonpredated and predated by ermines, and at random locations. We also determined winter nest density in 3 habitats (wet, mesic, and gully). Deep and hard snow restricted fox predation attempts made by jumping through the snow, but not those made by digging. Ermine predation was unaffected by snow depth and weakly by nest density but was higher in gully and intermediate in mesic habitats, which are conducive to high snow accumulation, compared to the wet habitat. These results indicate that habitat-related topographical features are more important than snow depth or nest density per se in affecting the winter foraging strategy of ermines. Overall, even though we found a relatively weak effect of the snow cover on predation by foxes and ermines, it is difficult to predict how upcoming changes to the snow cover will affect lemming vulnerability to mammalian predators because a wide range of snow conditions may result from climate warming. [ABSTRACT FROM AUTHOR]

Satellite telemetry can provide valuable information on spatial ecology of animals, especially in species inhabiting remote areas such as the Arctic. However, caution is always needed when selecting transmitter size and attachment methods because of the potential negative impact of the device itself on individuals. We determined survival and reproductive performance of adult female snowy owls ( Bubo scandiacus) tracked by satellite to evaluate potential adverse effects of transmitters. In summer 2007, we captured 12 adult females on their nest in the Canadian Arctic, marked them with 30-g harness-mounted transmitters, and tracked their movement for up to 3 years. All marked birds resumed normal activities shortly (<60 min) after release and none deserted their nest. We had 2 known deaths and 2 transmitters that stopped moving over 3 years, yielding an annual survival rate between 85.2 ± 7.0% and 92.3 ± 5.7%. Moreover, summer movement patterns, combined with ground checks in several cases, suggested that all successfully tracked birds initiated a nest every year after marking. Finally, laying date and clutch size of individuals did not differ before and after marking. Overall, our data indicate that life history traits of adult female snowy owls were not affected by satellite transmitters. © 2012 The Wildlife Society. [ABSTRACT FROM AUTHOR]

The article presents a study on the social interaction of Greater Snow Geese (Chen caerulescens atlantica). The researchers conducted the project in Bylot, Ellesmere and Axel Heiberg islands in Nunavut, Canada. They conclude that the birds form association during subsequent breeding seasons, but not during migration.

Abstract: The purpose of this paper is to emphasize the benefits of adopting non-destructive energy dispersive X-ray fluorescence (ED-XRF) as a first-order technique to determine chert whole-rock geochemistry for archaeological sourcing. Chemical signatures for the Touladi and La Martre prehistoric quarries from the lower St. Lawrence and Gaspé Peninsula region of Quebec, Canada, are determined and serve as references to test the provenance of regional chert artifacts. Chert experimental flakes, created from quarry geological hand samples, are analyzed and used to validate the method. Archaeological flakes and tools recovered from three archaeological sites are analyzed and tested against quarry samples. Geochemical diagrams and Principal Component Analysis are used to establish artifact-quarry relationships. The effects of surface weathering on the geochemical analysis of archaeological chert artifacts are presented. Sample restoration and research avenues are discussed and proposed to further enhance the robustness of future chert geochemical data sets. [Copyright &y& Elsevier]

Snow cover has dramatic effects on the structure and functioning of Arctic ecosystems in winter. In the tundra, the subnivean space is the primary habitat of wintering small mammals and may be critical for their survival and reproduction. We have investigated the effects of snow cover and habitat features on the distributions of collared lemming ( Dicrostonyx groenlandicus) and brown lemming ( Lemmus trimucronatus) winter nests, as well as on their probabilities of reproduction and predation by stoats ( Mustela erminea) and arctic foxes ( Vulpes lagopus). We sampled 193 lemming winter nests and measured habitat features at all of these nests and at random sites at two spatial scales. We also monitored overwinter ground temperature at a subsample of nest and random sites. Our results demonstrate that nests were primarily located in areas with high micro-topography heterogeneity, steep slopes, deep snow cover providing thermal protection (reduced daily temperature fluctuations) and a high abundance of mosses. The probability of reproduction increased in collared lemming nests at low elevation and in brown lemming nests with high availability of some graminoid species. The probability of predation by stoats was density dependent and was higher in nests used by collared lemmings. Snow cover did not affect the probability of predation of lemming nests by stoats, but deep snow cover limited predation attempts by arctic foxes. We conclude that snow cover plays a key role in the spatial structure of wintering lemming populations and potentially in their population dynamics in the Arctic. [ABSTRACT FROM AUTHOR]

Abstract: Baseline glucocorticoid (CORT) levels in plasma are increasingly used as physiological indices of the relative condition or health of individuals and populations. The major limitation is that CORT production is stimulated by the stress associated with capture and handling. Measuring fecal CORT is one way to solve this problem because elevation of fecal CORT usually does not occur before 1–12h after a stressful event in captive animals. However, the effect of capture and handling on fecal CORT levels has seldom been investigated in the wild. In a first experiment, we validated that fecal CORT levels starts to increase in droppings (a mixture of fecal and urinary material) about 1–2h following injection of CORT-release hormone (ACTH) in captive greater snow geese (Chen caerulescens atlantica). In a second experiment, we investigated whether dropping and plasma CORT were related and if the capture affected fecal CORT levels in wild birds. Baseline CORT was obtained by bleeding individuals within 4min after capture. No relationship was found between baseline and CORT in droppings shortly after capture (<4min). In addition, CORT levels in droppings increased linearly with time after capture and was already elevated by a factor two 40min after capture. The different turnover time of CORT between urine and feces could explain such results. We conclude that droppings cannot provide an index of basal CORT levels in snow geese captured in the wild. Such a result contrast with previous studies conducted on habituated, captive animals. We thus recommend that use of droppings as a non-invasive technique to measure baseline CORT be restricted to non-manipulated individuals in the wild. [Copyright &y& Elsevier]

Top predators of the arctic tundra are facing a long period of very low prey availability during winter and subsidies from other ecosystems such as the marine environment may help to support their populations. Satellite tracking of snowy owls, a top predator of the tundra, revealed that most adult females breeding in the Canadian Arctic overwinter at high latitudes in the eastern Arctic and spend several weeks (up to 101 d) on the sea-ice between December and April. Analysis of high-resolution satellite images of sea-ice indicated that owls were primarily gathering around open water patches in the ice, which are commonly used by wintering seabirds, a potential prey. Such extensive use of sea-ice by a tundra predator considered a small mammal specialist was unexpected, and suggests that marine resources subsidize snowy owl populations in winter. As sea-ice regimes in winter are expected to change over the next decades due to climate warming, this may affect the wintering strategy of this top predator and ultimately the functioning of the tundra ecosystem. [ABSTRACT FROM AUTHOR]

Winter breeding under the snow is a critical ecological adaptation of lemmings and a key demographic process in their periodic multiannual fluctuations in abundance. However, logistic constraints limit our ability to quantify lemming winter reproduction. We evaluated a method to infer lemming reproduction based on the size distribution of feces found in their winter nests. We determined criteria allowing identification of reproduction from feces found in nests, using golden Syrian hamsters (Mesocricetus auratus) as a surrogate model. We found a large difference in individual mass of feces between juveniles at weaning and adults. Using bimodal distribution of feces size, mean size difference, and proportion of small feces, we showed that visual inspection of ≥30 feces was sufficient to infer hamster reproduction with an accuracy of >95%.We also applied the method to winter nests of collared lemmings (Dicrostonyx groenlandicus) and brown lemmings (Lemmus trimucronatus) found in the Canadian Arctic. Because characteristics of feces found in lemming winter nests matched those found in hamster nests, we suggest that the method can be used to detect winter reproductive activity of lemmings. [ABSTRACT FROM AUTHOR]

Abstract: CeLSCM (CexLa0.75−xSr0.25Cr0.5Mn0.5O3) materials were synthesized for x=0, 0.10, 0.25 and 0.375. Structural, physico-chemical and electrical properties are compared to La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM). For x≤0.25, these oxides exhibit a rhombohedral symmetry (space group Rc), whereas the structure is cubic (Pmm) for x=0.375. All those materials are stable in both elaboration and operating conditions of an SOFC anode. They are also stable in steam electrolysis (SOEC) cathodic conditions. Exposure to air yields the formation of CeO2 for cerium containing materials, and decomposition into a Ruddlesden Popper phase type chromo-manganite occurs in dry H2 both for CeLSCM series and pure LSCM. In dry argon, wet argon and wet hydrogen, these materials are p-type semi-conductors. Electrical conductivity increases with cerium content in argon and reaches 35S·cm−1 at 900°C. In wet hydrogen (H2-3% H2O), the total conductivity is about 1S·cm−1 at 900°C, regardless the cerium content, which is regarded as not so detrimental for the application. [Copyright &y& Elsevier]

1. Dispersal is a fundamental but still poorly known process in population dynamics and several hypotheses have been proposed to explain its patterns. We studied natal and breeding dispersal and survival in a long-lived seabird, the wandering albatross ( Diomedea exulans L.), and examined several hypotheses concerning dispersal patterns in birds. 2. We applied multi-state capture–recapture models to a 36-year data set (1969–2004) collected at three albatross colonies on Île de Possession, Crozet Islands. Because the species has biennial reproduction, we introduced unobservable states in the model to account for the absence of individuals in those years. 3. Adults were highly faithful to their nesting colony but colony fidelity, as well as survival rate, differed slightly among colonies (fidelity ranged from 0·957 to 0·977). Breeding fidelity was highest in the colony where survival was lowest and individuals were not more likely to change colony following a failed breeding attempt than after a successful one. The colony that attracted most dispersers had the lowest density of nesting birds. 4. Philopatry (the probability that young return to breed at a birth site) was generally high but variable among colonies (ranging from 0·70 to 0·92), and survival of young differed little. Philopatry was highest in the largest colony, where the availability of potential mates was presumably greatest. However, among dispersing individuals, the colony that had the lowest density of nesting individuals, not the largest colony, attracted the most recruits. 5. Although size of the colony influenced the decision to stay or to leave in young, density was most influential in the selection of a new colony among both adult and young dispersers. Our results support the hypothesis that philopatry is the strategy favoured by most recruits and that conspecific attraction can explain variation in the level of philopatry among colonies but not settlement patterns among dispersing individuals. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFC) are promising devices for high efficiency cogeneration. The most widely used and studied ones have an anion conducting electrolyte that requires high operating temperatures to limit ohmic losses across this electrolyte; temperatures typically range between 800 and 1,000 °C. This temperature is associated with undesirable phenomena such as material interaction and insulating phase formation that result in unsatisfactory durability and high cost for market entry. Proton conducting solid oxide fuel cells (PCFC) constitutes a promising alternative since they allow a significant decrease in operating temperature. The Ba(Zr,Ce,Ln)O3−δ perovskite family exhibits ionic conductivities reaching 10−2 to 10−1 S cm−1 at temperatures as low as 600–700 °C, these values being obtained with anion conducting SOFC between 700 and 1,000 °C. On the basis of a review of work on half cells and complete cells, this paper addresses the main parameters that control and limit PCFC behaviour. This analysis aims at proposing recommendations for designing and testing proton conducting fuel cells. [ABSTRACT FROM AUTHOR]

Nonrandom dispersal has been recently advanced as a mechanism promoting fine-scale genetic differentiation in resident populations, yet how this applies to species with high rates of dispersal is still unclear. Using a migratory species considered a classical example of male-biased dispersal (the greater snow goose, Chen caerulescens atlantica), we documented a temporally stable fine-scale genetic clustering between spatially distinct rearing sites (5–30 km apart), where family aggregates shortly after hatching. Such genetic differentiation can only arise if, in both sexes, dispersal is restricted and nonrandom, a surprising result considering that pairing occurs among mixed flocks of birds more than 3000 km away from the breeding grounds. Fine-scale genetic structure may thus occur even in migratory species with high gene flow. We further show that looking for genetic structure based on nesting sites only may be misleading. Genetically distinct individuals that segregated into different rearing sites were in fact spatially mixed during nesting. These findings provide new, scale-dependent links between genetic structure, pairing, and dispersal and show the importance of sampling different stages of the breeding cycle in order to detect a spatial genetic structure. [ABSTRACT FROM AUTHOR]

Although water availability is primarily seen as a factor affecting food availability (a bottom-up process), we examined its effect on predator-prey interactions through an influence on prey behavior (a top-down process). We documented a link between water availability, predation risk, and reproductive success in a goose species (Chen caerulescens atlantica) inhabiting an Arctic environment where water is not considered a limited commodity. To reach water sources during incubation recesses, geese nesting in mesic tundra (low water availability) must move almost four times as far from their nest than those nesting in wetlands, which reduced their ability to defend their nest against predators and led to a higher predation rate. Nesting success was improved in high rainfall years due to increased water availability, and more so for geese nesting in the low water availability habitat. Likewise, nesting success was improved in years where the potential for evaporative water loss (measured by the atmospheric water vapor pressure) was low, presumably because females had to leave their nest less often to drink. Females from water-supplemented nests traveled a shorter distance to drink, and their nesting success was enhanced by 20% compared to the control. This shows that water availability and rainfall can have a strong effect on predator-prey dynamics and that changes in precipitation brought by climate change could have an impact on some Arctic species through a top-down effect. [ABSTRACT FROM AUTHOR]

Common Goldeneyes (Bucephala clangula) and Hooded Mergansers (Lophodytes cucullatus) are common cavity-nesting ducks but the importance of fast-flowing rivers as suitable nesting habitat may have been overlooked. We monitored the use of >90 nest boxes installed along a boreal forest river over a 5-year period. A high nest box occupancy rate was reached in the second year (40%) and was maintained thereafter (48 to 55%). On average, 35 nest boxes were occupied by goldeneyes and 11 by mergansers each year. Laying date was similar between the two species but merganser nests hatched slightly later. Both species bad similar clutch sizes but merganser nests contained more eggs than goldeneye nests when heterospecific parasitic eggs were included. On average, 16% of goldeneye nests were parasitized by mergansers, and 49% of merganser nests were parasitized by goldeneyes. Density of suitable natural cavities in the area was relatively low suggesting the high occupancy rate of nest boxes may be a response to lack of suitable cavities. Nest box use was positively related to the total surface area of ponds in the vicinity and negatively to distance to the river. Use of nest sites along fast-flowing rivers appears to be an opportunistic strategy and may be dependant on the presence of nearby ponds and lakes. [ABSTRACT FROM AUTHOR]