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Gilles Gauthier - One of the best experts on this subject based on the ideXlab platform.
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the greater Snow Goose anser caerulescens atlanticus managing an overabundant population
AMBIO: A Journal of the Human Environment, 2017Co-Authors: Josee Lefebvre, Gilles Gauthier, Jeanfrancois Giroux, Austin Reed, Eric T Reed, Luc BelangerAbstract: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.
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Appendix C. Multi-event modeling of survival, breeding propensity, nesting success, recapture, resighting, and recovery probabilities in the Greater Snow Goose.
2016Co-Authors: Guillaume Souchay, Gilles Gauthier, Roger PradelAbstract:Multi-event modeling of survival, breeding propensity, nesting success, recapture, resighting, and recovery probabilities in the Greater Snow Goose
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long term monitoring at multiple trophic levels suggests heterogeneity in responses to climate change in the canadian arctic tundra
Philosophical Transactions of the Royal Society B, 2013Co-Authors: Gilles Gauthier, Joel Bety, Mariechristine Cadieux, Pierre Legagneux, Madeleine Doiron, Clement Chevallier, Arnaud Tarroux, Dominique BerteauxAbstract: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.
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a capture recapture model with double marking live and dead encounters and heterogeneity of reporting due to auxiliary mark loss
Journal of Agricultural Biological and Environmental Statistics, 2011Co-Authors: C Juillet, Gilles Gauthier, Remi Choquet, Roger PradelAbstract:Capture–recapture (CR) models assume marked individuals remain at risk of capture, which may not be true if individuals lose their mark or emigrate definitively from the study area. Using a double-marking protocol, with a main and auxiliary mark, and both live encounters and dead recoveries at a large scale, partially frees CR models from this assumption. However, the auxiliary mark may fall off and its presence is often not mentioned when dead individuals are reported. We propose a new model to deal with heterogeneity of detection and uncertainty of the presence of an auxiliary mark in a multi-event framework. Our general model, based on a double-marking protocol, uses information from physical captures/recaptures, distant observations and main mark recoveries from dead animals. We applied our model to a 13-year data set of a harvested species, the Greater Snow Goose. We obtained seasonal survival estimates for adults of both sexes. Survival estimates differed between models where the presence of the auxiliary mark upon recovery was ignored versus those where the presence was accounted for. In the multi-event framework, seasonal survival estimates are no longer biased because the heterogeneity due to the presence of an auxiliary mark is accounted for in the estimation of recovery rates. Note: An illustration of the implementation of our model in E-SURGE is available online.
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climate trophic interactions density dependence and carry over effects on the population productivity of a migratory arctic herbivorous bird
Oikos, 2010Co-Authors: Manon Morrissette, Gilles Gauthier, Joel Bety, Austin Reed, Josee LefebvreAbstract:Several driving forces can aff ect recruitment rates in bird populations. However, our understanding of climate-induced eff ects or bottom–up vs top–down biological processes on breeding productivity typically comes from small-scale studies, and their relative importance is rarely investigated at the population level. Using a 31-year time series, we examined the eff ects of selected environmental parameters on the annual productivity of a key Arctic herbivore, the greater Snow Goose Anser caerulescens atlanticus. We determined the extent to which breeding productivity, defi ned as the percentage of juveniles in the fall population, was aff ected by 1) climatic conditions, 2) fl uctuations in predation pressure caused by small rodent oscillations, and 3) population size. Moreover, we took advantage of an unplanned large-scale manipulation (i.e. management action) to examine the potential non-lethal carry-over eff ects caused by disturbance on spring staging sites. Th e most parsimonious model explained 66% of the annual variation in Goose productivity. Th e spring North Atlantic Oscillation and Arctic Snow depth were the primary climatic parameters inversely aff ecting the production of juveniles, likely through bottom–up processes. Indirect trophic interactions generated by fl uctuations in lemming abundance explained 18% of the variation in Goose productivity (positive relationship). Mean temperature during brood-rearing and disturbance on staging sites (carry-over eff ects) were the other important factors aff ecting population recruitment. We observed a strong population increase, and found no evidence of density-dependent eff ects. Spatially restricted studies can identify factors linking environmental parameters to local bird reproduction but if these factors do not act synchronously over the species range, they may fail to identify the relative importance of mechanisms driving large-scale population dynamics.
Jeanfrancois Giroux - One of the best experts on this subject based on the ideXlab platform.
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the greater Snow Goose anser caerulescens atlanticus managing an overabundant population
AMBIO: A Journal of the Human Environment, 2017Co-Authors: Josee Lefebvre, Gilles Gauthier, Jeanfrancois Giroux, Austin Reed, Eric T Reed, Luc BelangerAbstract: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.
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ARCTIC Habitat Use by Greater Snow Geese During the Brood-Rearing Period
2015Co-Authors: Jeanfrancois GirouxAbstract:ABSTRACT. Observations of habitat use by the Greater Snow Goose (Anser caerulescens atlanricus) were conducted at Jungersen Bay, northern Baffin Island, from 27 July- 17 August 1981. Density of geese using the study area was estimated at 425 birds.km-2. The average of 2.8 young per family did not change during our study. Non-breeding geese were first observed in flight on I August and were seen regularly until 13 August. Three types of habitat used by geese during the brood-rearing period were distinguished: tidal marshes dominated by Carex subsparhacea and Puccinellia phryganodes; wet moss-covered meadows with up to 5 cm of standing water, dominated by Carex srans, Duponriafisheri, Calamagrosris neglecra, and Arctagrosris latifolia; and, around ponds, bands of vegetation 1-2 m wide dominated by Carex srans. The three most important species of monocots grazed by geese were Puccinelliaphrygwwdes, Carex subspathacea, and C. srans. It is unlikely that habitat and food resources are limiting factors for Greater Snow Geese in the High Arctic during the brood-rearing period. We suggest that potential breeding areas for this species be iden-tified and given special protection
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ORIGINAL PAPER Cache and carry: hoarding behavior of arctic fox
2014Co-Authors: Dominique Berteaux, Jeanfrancois Giroux, Vincent Careau, -f. J. GirouxAbstract:Abstract Food-hoarding animals are expected to preferentially cache items with lower perishability and/or higher consumption time. We observed arctic foxes (Alopex lagopus) foraging in a greater Snow Goose (Anser caerulescens atlanticus) colony where the main prey of foxes consisted of Goose eggs, goslings, and lemmings (Lemmus and Dicrostonyx spp.). We recorded the number of prey consumed and cached and the time that foxes invested in these activities. Foxes took more time to consume a Goose egg than a lemming or gosling but cached a greater proportion of eggs than the other prey type. This may be caused by the eggshell, which presumably decreases the perishability and/or pilfering risk of cached eggs, but also increases egg consumption time. Arctic foxes usually Communicated by E. Korpimäk
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cache and carry hoarding behavior of arctic fox
Behavioral Ecology and Sociobiology, 2007Co-Authors: Vincent Careau, Jeanfrancois Giroux, Dominique BerteauxAbstract:Food-hoarding animals are expected to preferentially cache items with lower perishability and/or higher consumption time. We observed arctic foxes (Alopex lagopus) foraging in a greater Snow Goose (Anser caerulescens atlanticus) colony where the main prey of foxes consisted of Goose eggs, goslings, and lemmings (Lemmus and Dicrostonyx spp.). We recorded the number of prey consumed and cached and the time that foxes invested in these activities. Foxes took more time to consume a Goose egg than a lemming or gosling but cached a greater proportion of eggs than the other prey type. This may be caused by the eggshell, which presumably decreases the perishability and/or pilfering risk of cached eggs, but also increases egg consumption time. Arctic foxes usually recached Goose eggs but rarely recached goslings or lemmings. We tested whether the rapid-sequestering hypothesis could explain this recaching behavior. According to this hypothesis, arctic foxes may adopt a two-stage strategy allowing both to maximize egg acquisition rate in an undefended nest and subsequently secure eggs in potentially safer sites. Foxes spent more time carrying an egg and traveled greater distances when establishing a secondary than a primary cache. To gain further information on the location and subsequent fate of cached eggs, we used dummy eggs containing radio transmitters. Lifespan of primary caches increased with distance from the Goose nest. Secondary caches were generally located farther from the nest and had a longer lifespan than primary caches. Behavioral observations and the radio-tagged egg technique both gave results supporting the rapid-sequestering hypothesis.
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Individual variation in timing of migration: causes and reproductive consequences in greater Snow geese (Anser caerulescens atlanticus)
Behavioral Ecology and Sociobiology, 2004Co-Authors: Joel Bety, Jeanfrancois Giroux, Gilles GauthierAbstract:Decisions made by birds during migration to breeding grounds can strongly affect the fitness of individuals. We investigated possible causes and reproductive consequences of inter-individual variation in the migratory behavior of an arctic-nesting species, the greater Snow Goose ( Anser caerulescens atlanticus ), by radio-tracking females at their staging area and on their breeding grounds. Females showed relatively high repeatability in the duration of migration (r_i=0.37) and arrival date on the breeding grounds (r_i=0.42) suggesting that these traits are characteristics of individuals. Conversely, no individual consistency in departure date from the staging area was detected (r_i=−0.02) indicating that environmental factors may have a large influence. Females paired with dominant males departed slightly earlier from the staging area than females accompanied by subordinate males. However, neither social status on the staging area (i.e. paired vs unpaired) nor dominance scores were associated with arrival time of individuals. Finally, the probability of breeding was positively related to arrival date indicating a reproductive cost of arriving too early on the breeding grounds. The combination of breeding probability and seasonal decline in breeding success nonetheless suggests that females arriving a few days earlier than the median arrival date attained highest reproductive success. Our results show that assessing the fitness consequences of early arrival by focusing solely on breeding females would lead to an overestimation of the genuine benefits. This study also indicates possible genetically based differences among individuals in migration duration and arrival time on the breeding grounds.
Robert F Rockwell - One of the best experts on this subject based on the ideXlab platform.
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a comparison of drone imagery and ground based methods for estimating the extent of habitat destruction by lesser Snow geese anser caerulescens caerulescens in la perouse bay
PLOS ONE, 2019Co-Authors: Andrew Barnas, Robert F Rockwell, Brian J Darby, Gregory S Vandeberg, Susan N EllisfelegeAbstract:Lesser Snow Goose (Anser caerulescens caerulescens) populations have dramatically altered vegetation communities through increased foraging pressure. In remote regions, regular habitat assessments are logistically challenging and time consuming. Drones are increasingly being used by ecologists to conduct habitat assessments, but reliance on georeferenced data as ground truth may not always be feasible. We estimated Goose habitat degradation using photointerpretation of drone imagery and compared estimates to those made with ground-based linear transects. In July 2016, we surveyed five study plots in La Perouse Bay, Manitoba, to evaluate the effectiveness of a fixed-wing drone with simple Red Green Blue (RGB) imagery for evaluating habitat degradation by Snow geese. Ground-based land cover data was collected and grouped into barren, shrub, or non-shrub categories. We compared estimates between ground-based transects and those made from unsupervised classification of drone imagery collected at altitudes of 75, 100, and 120 m above ground level (ground sampling distances of 2.4, 3.2, and 3.8 cm respectively). We found large time savings during the data collection step of drone surveys, but these savings were ultimately lost during imagery processing. Based on photointerpretation, overall accuracy of drone imagery was generally high (88.8% to 92.0%) and Kappa coefficients were similar to previously published habitat assessments from drone imagery. Mixed model estimates indicated 75m drone imagery overestimated barren (F2,182 = 100.03, P < 0.0001) and shrub classes (F2,182 = 160.16, P < 0.0001) compared to ground estimates. Inconspicuous graminoid and forb species (non-shrubs) were difficult to detect from drone imagery and were underestimated compared to ground-based transects (F2,182 = 843.77, P < 0.0001). Our findings corroborate previous findings, and that simple RGB imagery is useful for evaluating broad scale Goose damage, and may play an important role in measuring habitat destruction by geese and other agents of environmental change.
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Effects of exploitation on an overabundant species: the lesser Snow Goose predicament
2016Co-Authors: David N Koons, Robert F Rockwell, Lise M AubryAbstract:1. Invasive and overabundant species are an increasing threat to biodiversity and ecosystem functioning world-wide. As such, large amounts of money are spent each year on attempts to control them. These efforts can, however, be thwarted if exploitation is compensated demo-graphically or if populations simply become too numerous for management to elicit an effective and rapid functional response. 2. We examined the influence of these mechanisms on cause-specific mortality in lesser Snow geese using multistate capture–reencounter methods. The abundance and destructive foraging behaviours of Snow geese have created a trophic cascade that reduces (sub-) Arctic plant, insect and avian biodiversity, bestowing them the status of ‘overabundant’. 3. Historically, juvenile Snow geese suffered from density-related degradation of their saltmarsh brood-rearing habitat. This allowed harvest mortality to be partially compensated by non-harvest mortality (process correlation between mortality sources: q = 047; 90 % BCI: 072 to 004). Snow Goose family groups eventually responded to their own degradation of habitat by dispersing to non-degraded areas. This relaxed the pressure of density dependence on juvenile birds, but without this mechanism for compensation, harvest began to have an additive effec
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Part of the Life Sciences Commons
2014Co-Authors: Robert F Rockwell, David N Koons, Lise M AubryAbstract:Effects of exploitation on an overabundant species: the lesser Snow Goose predicamen
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Climate change, phenology, and habitat degradation: drivers of gosling body condition and juvenile survival in lesser Snow geese
Global Change Biology, 2012Co-Authors: Lise M Aubry, Evan G Cooch, Christa P. H. Mulder, Rodney W Brook, Robert F Rockwell, David N KoonsAbstract:Nesting migratory geese are among the dominant herbivores in (sub) arctic environments, which have undergone unprecedented increases in temperatures and plant growing days over the last three decades. Within these regions, the Hudson Bay Lowlands are home to an overabundant breeding population of lesser Snow geese that has dramatically damaged the ecosystem, with cascading effects at multiple trophic levels. In some areas the overabundance of geese has led to a drastic reduction in available forage. In addition, warming of this region has widened the gap between Goose migration timing and plant green-up, and this ‘mismatch’ between Goose and plant phenologies could in turn affect gosling development. The dual effects of climate change and habitat quality on gosling body condition and juvenile survival are not known, but are critical for predicting population growth and related degradation of (sub) arctic ecosystems. To address these issues, we used information on female goslings marked and measured between 1978 and 2005 (4125 individuals). Goslings that developed within and near the traditional center of the breeding colony experienced the effects of long-term habitat degradation: body condition and juvenile survival declined over time. In newly colonized areas, however, we observed the opposite pattern (increase in body condition and juvenile survival). In addition, warmer than average winters and summers resulted in lower gosling body condition and first-year survival. Too few plant ‘growing days’ in the spring relative to hatch led to similar results. Our assessment indicates that geese are recovering from habitat degradation by moving to newly colonized locales. However, a warmer climate could negatively affect Snow Goose populations in the long-run, but it will depend on which seasons warm the fastest. These antagonistic mechanisms will require further study to help predict Snow Goose population dynamics and manage the trophic cascade they induce.
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Trophic matches and mismatches: can polar bears reduce the abundance of nesting Snow geese in western Hudson Bay
2011Co-Authors: Robert F Rockwell, Linda J. Gormezano, David N KoonsAbstract:Climate change driven advances in the date of sea ice breakup will increasingly lead to a loss of spring polar bear foraging opportunities on ringed seal pups creating a phenological trophic ' mismatch ' . However, the same shift will lead to a new ' match ' between polar bears and ground nesting birds. Th is new match will be especially prevalent along the Cape Churchill Peninsula of western Hudson Bay where both polar bears and nesting Snow geese are abundant. Easily foraged Goose eggs will provide at least some of the earlier arriving polar bears with compensation for the energy defi cit accrued through lost seal hunting opportunities. We examine the potential impact of changes in the extent and pattern of polar bear egg predation on Snow Goose abundance using projection models that account not only for increases in the temporal overlap of the two species but also for autocorrelation and stochasticity in the processes underlying polar bear onshore arrival and Snow Goose incubation. Egg predation will reduce reproductive output of the nesting lesser Snow geese and, under all but trivial rates, will lead to a reduction in the size of their nesting population on the Cape Churchill Peninsula. Stochasticity associated with the asymmetrical advances in polar bear onshore arrival and the Snow Goose incubation period will lead to periodic mismatches in their overlap. Th ese, in turn, will allow Snow Goose abundance to increase periodically. Climate driven changes in trophic matches and mismatches may reduce Snow Goose numbers but will not eliminate this over-abundant species that poses a threat to Arctic landscapes
Joel Bety - One of the best experts on this subject based on the ideXlab platform.
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long term monitoring at multiple trophic levels suggests heterogeneity in responses to climate change in the canadian arctic tundra
Philosophical Transactions of the Royal Society B, 2013Co-Authors: Gilles Gauthier, Joel Bety, Mariechristine Cadieux, Pierre Legagneux, Madeleine Doiron, Clement Chevallier, Arnaud Tarroux, Dominique BerteauxAbstract: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.
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climate trophic interactions density dependence and carry over effects on the population productivity of a migratory arctic herbivorous bird
Oikos, 2010Co-Authors: Manon Morrissette, Gilles Gauthier, Joel Bety, Austin Reed, Josee LefebvreAbstract:Several driving forces can aff ect recruitment rates in bird populations. However, our understanding of climate-induced eff ects or bottom–up vs top–down biological processes on breeding productivity typically comes from small-scale studies, and their relative importance is rarely investigated at the population level. Using a 31-year time series, we examined the eff ects of selected environmental parameters on the annual productivity of a key Arctic herbivore, the greater Snow Goose Anser caerulescens atlanticus. We determined the extent to which breeding productivity, defi ned as the percentage of juveniles in the fall population, was aff ected by 1) climatic conditions, 2) fl uctuations in predation pressure caused by small rodent oscillations, and 3) population size. Moreover, we took advantage of an unplanned large-scale manipulation (i.e. management action) to examine the potential non-lethal carry-over eff ects caused by disturbance on spring staging sites. Th e most parsimonious model explained 66% of the annual variation in Goose productivity. Th e spring North Atlantic Oscillation and Arctic Snow depth were the primary climatic parameters inversely aff ecting the production of juveniles, likely through bottom–up processes. Indirect trophic interactions generated by fl uctuations in lemming abundance explained 18% of the variation in Goose productivity (positive relationship). Mean temperature during brood-rearing and disturbance on staging sites (carry-over eff ects) were the other important factors aff ecting population recruitment. We observed a strong population increase, and found no evidence of density-dependent eff ects. Spatially restricted studies can identify factors linking environmental parameters to local bird reproduction but if these factors do not act synchronously over the species range, they may fail to identify the relative importance of mechanisms driving large-scale population dynamics.
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Individual variation in timing of migration: causes and reproductive consequences in greater Snow geese (Anser caerulescens atlanticus)
Behavioral Ecology and Sociobiology, 2004Co-Authors: Joel Bety, Jeanfrancois Giroux, Gilles GauthierAbstract:Decisions made by birds during migration to breeding grounds can strongly affect the fitness of individuals. We investigated possible causes and reproductive consequences of inter-individual variation in the migratory behavior of an arctic-nesting species, the greater Snow Goose ( Anser caerulescens atlanticus ), by radio-tracking females at their staging area and on their breeding grounds. Females showed relatively high repeatability in the duration of migration (r_i=0.37) and arrival date on the breeding grounds (r_i=0.42) suggesting that these traits are characteristics of individuals. Conversely, no individual consistency in departure date from the staging area was detected (r_i=−0.02) indicating that environmental factors may have a large influence. Females paired with dominant males departed slightly earlier from the staging area than females accompanied by subordinate males. However, neither social status on the staging area (i.e. paired vs unpaired) nor dominance scores were associated with arrival time of individuals. Finally, the probability of breeding was positively related to arrival date indicating a reproductive cost of arriving too early on the breeding grounds. The combination of breeding probability and seasonal decline in breeding success nonetheless suggests that females arriving a few days earlier than the median arrival date attained highest reproductive success. Our results show that assessing the fitness consequences of early arrival by focusing solely on breeding females would lead to an overestimation of the genuine benefits. This study also indicates possible genetically based differences among individuals in migration duration and arrival time on the breeding grounds.
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body condition migration and timing of reproduction in Snow geese a test of the condition dependent model of optimal clutch size
The American Naturalist, 2003Co-Authors: Joel Bety, Gilles Gauthier, Jeanfrancois GirouxAbstract:Abstract: The seasonal decline of avian clutch size may result from the conflict between the advantage of early breeding (greater offspring value) and the advantage of a delay in lay date (improved body condition and hence clutch size). We tested predictions of a condition‐dependent individual optimization model based on this trade‐off (Rowe et al. 1994) in a long‐distance migrant, the greater Snow Goose (Chen caerulescens atlantica), using data on condition, migration, and reproductive decisions of individuals. We closely tracked radio‐marked females at their main spring staging area and on their breeding grounds. Our results were consistent with predictions of the model. Early‐arriving females had a longer prelaying period and initiated their nests earlier than late arrivals. After controlling statistically for arrival date, we determined that females with high premigration condition had an earlier lay date than those in low condition. After controlling for the seasonal decline (i.e., lay date), we obse...
David N Koons - One of the best experts on this subject based on the ideXlab platform.
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Effects of exploitation on an overabundant species: the lesser Snow Goose predicament
2016Co-Authors: David N Koons, Robert F Rockwell, Lise M AubryAbstract:1. Invasive and overabundant species are an increasing threat to biodiversity and ecosystem functioning world-wide. As such, large amounts of money are spent each year on attempts to control them. These efforts can, however, be thwarted if exploitation is compensated demo-graphically or if populations simply become too numerous for management to elicit an effective and rapid functional response. 2. We examined the influence of these mechanisms on cause-specific mortality in lesser Snow geese using multistate capture–reencounter methods. The abundance and destructive foraging behaviours of Snow geese have created a trophic cascade that reduces (sub-) Arctic plant, insect and avian biodiversity, bestowing them the status of ‘overabundant’. 3. Historically, juvenile Snow geese suffered from density-related degradation of their saltmarsh brood-rearing habitat. This allowed harvest mortality to be partially compensated by non-harvest mortality (process correlation between mortality sources: q = 047; 90 % BCI: 072 to 004). Snow Goose family groups eventually responded to their own degradation of habitat by dispersing to non-degraded areas. This relaxed the pressure of density dependence on juvenile birds, but without this mechanism for compensation, harvest began to have an additive effec
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Part of the Life Sciences Commons
2014Co-Authors: Robert F Rockwell, David N Koons, Lise M AubryAbstract:Effects of exploitation on an overabundant species: the lesser Snow Goose predicamen
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Climate change, phenology, and habitat degradation: drivers of gosling body condition and juvenile survival in lesser Snow geese
Global Change Biology, 2012Co-Authors: Lise M Aubry, Evan G Cooch, Christa P. H. Mulder, Rodney W Brook, Robert F Rockwell, David N KoonsAbstract:Nesting migratory geese are among the dominant herbivores in (sub) arctic environments, which have undergone unprecedented increases in temperatures and plant growing days over the last three decades. Within these regions, the Hudson Bay Lowlands are home to an overabundant breeding population of lesser Snow geese that has dramatically damaged the ecosystem, with cascading effects at multiple trophic levels. In some areas the overabundance of geese has led to a drastic reduction in available forage. In addition, warming of this region has widened the gap between Goose migration timing and plant green-up, and this ‘mismatch’ between Goose and plant phenologies could in turn affect gosling development. The dual effects of climate change and habitat quality on gosling body condition and juvenile survival are not known, but are critical for predicting population growth and related degradation of (sub) arctic ecosystems. To address these issues, we used information on female goslings marked and measured between 1978 and 2005 (4125 individuals). Goslings that developed within and near the traditional center of the breeding colony experienced the effects of long-term habitat degradation: body condition and juvenile survival declined over time. In newly colonized areas, however, we observed the opposite pattern (increase in body condition and juvenile survival). In addition, warmer than average winters and summers resulted in lower gosling body condition and first-year survival. Too few plant ‘growing days’ in the spring relative to hatch led to similar results. Our assessment indicates that geese are recovering from habitat degradation by moving to newly colonized locales. However, a warmer climate could negatively affect Snow Goose populations in the long-run, but it will depend on which seasons warm the fastest. These antagonistic mechanisms will require further study to help predict Snow Goose population dynamics and manage the trophic cascade they induce.
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Trophic matches and mismatches: can polar bears reduce the abundance of nesting Snow geese in western Hudson Bay
2011Co-Authors: Robert F Rockwell, Linda J. Gormezano, David N KoonsAbstract:Climate change driven advances in the date of sea ice breakup will increasingly lead to a loss of spring polar bear foraging opportunities on ringed seal pups creating a phenological trophic ' mismatch ' . However, the same shift will lead to a new ' match ' between polar bears and ground nesting birds. Th is new match will be especially prevalent along the Cape Churchill Peninsula of western Hudson Bay where both polar bears and nesting Snow geese are abundant. Easily foraged Goose eggs will provide at least some of the earlier arriving polar bears with compensation for the energy defi cit accrued through lost seal hunting opportunities. We examine the potential impact of changes in the extent and pattern of polar bear egg predation on Snow Goose abundance using projection models that account not only for increases in the temporal overlap of the two species but also for autocorrelation and stochasticity in the processes underlying polar bear onshore arrival and Snow Goose incubation. Egg predation will reduce reproductive output of the nesting lesser Snow geese and, under all but trivial rates, will lead to a reduction in the size of their nesting population on the Cape Churchill Peninsula. Stochasticity associated with the asymmetrical advances in polar bear onshore arrival and the Snow Goose incubation period will lead to periodic mismatches in their overlap. Th ese, in turn, will allow Snow Goose abundance to increase periodically. Climate driven changes in trophic matches and mismatches may reduce Snow Goose numbers but will not eliminate this over-abundant species that poses a threat to Arctic landscapes
