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James S Sedinger - One of the best experts on this subject based on the ideXlab platform.
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Growth of black brant and lesser snow goose Goslings in northern alaska
The Journal of Wildlife Management, 2017Co-Authors: Jerry W. Hupp, James S Sedinger, David H. Ward, Kyle R. Hogrefe, Philip D. Martin, Alice A. Stickney, Tim ObritschkewitschAbstract:Gosling body mass can affect first year survival, recruitment, adult body size, and future fecundity of geese, and can serve as an indicator of forage availability and quality on brood-rearing areas. From 2012–2014 we measured body mass of 76 black brant (Branta bernicla nigricans) and 268 lesser snow goose (Chen caerulescens caerulescens) Goslings of known age on the Colville River Delta (CRD) of northern Alaska to determine if there was evidence of density-dependent declines in gosling growth following recent population increases of those species and sympatric greater white-fronted geese (Anser albifrons frontalis). We contrasted contemporary body mass of brant Goslings and forage biomass in brood-rearing habitats that were shared by all species, with measures obtained on, and near the CRD in the 1990s, prior to the establishment of snow goose nesting colonies in the area. Body mass of brant Goslings recaptured between 25 and 32 days of age had not changed over the past 2 decades, despite an influx of snow geese, and increases in populations of brant and white-fronted geese. At 30 days of age, body mass of brant Goslings on the CRD was 100–400 g heavier than for brant Goslings of the same age on the Yukon-Kuskokwim Delta (YKD), Alaska. Contemporary biomass of grazed Carex subspathacea on CRD brood-rearing areas was comparable to the 1990s and was 2–4 times greater than for the same plant community on the YKD. Historical data on growth of snow goose Goslings were not available for the CRD. However, average body mass of 34-day-old snow goose Goslings was >230 g heavier than for conspecifics of the same age in the Hudson Bay region. We conclude that the establishment of nesting snow geese on the CRD has not negatively affected brant gosling growth, and that recent population increases of all species have likely not been constrained by forage availability on brood-rearing areas. Barring demographic changes elsewhere in their annual cycles, we predict that goose populations will continue to increase in northern Alaska. However, snow geese are increasing more rapidly than brant in the region. Because the black brant population has periodically been below conservation objectives, the effects of the increasing number of snow geese on forage biomass and growth of brant Goslings in northern Alaska should be monitored. © 2017 The Wildlife Society.
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Are there trade-offs between pre- and post-fledging survival in black brent geese?
The Journal of animal ecology, 2012Co-Authors: Christopher A. Nicolai, James S SedingerAbstract:Summary 1. The growth period is an important determinant of fitness later in life through its effects on first-year survival and future reproduction. Choices by adult females about where to rear their offspring strongly affect growth rates and offspring fitness in geese. 2. Individual female black brent (Branta bernicla nigricans) tend to raise their broods in the same areas each year, and these areas are consistently ranked with respect to growth rates of Goslings. Therefore, some females consistently rear their broods on areas resulting in lower post-fledging fitness. 3. We explore the potential that growth rates of offspring (and associated fitness consequences) are traded off against other vital rates influencing fitness of either adult females or Goslings. Growth of Goslings primarily influences fitness after fledging, so one hypothesis is that survival before fledging, which is influenced by predation, is traded off against growth rates and post-fledging survival. 4. We estimated pre-fledging and post-fledging survival for Goslings reared on areas used by broods from the Tutakoke River black brent colony. We examined recaptures, recoveries by hunters and resightings of brent marked as Goslings with webtags and standard leg rings. These data were analyzed using capture–mark–recapture models in program mark to derive separate estimates of pre- and post-fledging survival for 18 cohorts (1987–2004) of black brent Goslings across seven brood rearing areas (BRAs). 5. Estimates of pre-fledging survival probability varied from 0·00 ± 0·00 (mean ± 95% confidence interval) to 0·92 ± 0·1; and estimates of post-fledging survival probability varied from 0·00 ± 0·00 to 1·00 ± 0·08. Substantial variation existed both among BRAs and years but post-fledging survival declined substantially during the study. 6. Pre- and post-fledging survival were positively correlated, exhibiting a quadratic relationship (spost-fledging survival = 1·00 (±0·47)x−0·83 (±0·480)x2, where x = pre-fledging survival). Therefore, we did not find a trade-off between pre- and post-fledging survival in black brent Goslings across BRAs, suggesting that factors other than foraging conditions and predation on Goslings must influence selection of BRAs.
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Intercolony variation in growth of black brant Goslings on the Yukon‐Kuskokwim Delta, Alaska
The Journal of Wildlife Management, 2011Co-Authors: Thomas F. Fondell, Paul L Flint, James S Sedinger, Christopher A. Nicolai, Jason L. SchamberAbstract:ABSTRACT Recent declines in black brant (Branta bernicla nigricans) are likely the result of low recruitment. In geese, recruitment is strongly affected by habitat conditions experienced by broods because gosling growth rates are indicative of forage conditions during brood rearing and strongly influence future survival and productivity. In 2006–2008, we studied gosling growth at 3 of the 4 major colonies on the YukonKuskokwim Delta, Alaska. Estimates of age-adjusted gosling mass at the 2 southern colonies (approx. 30% of the world population of breeding black brack) was low (gosling mass at 30.5 days ranged 346.7 ± 42.5 g to 627.1 ± 15.9 g) in comparison to a third colony (gosling mass at 30.5 days ranged 640.0 ± 8.3 g to 821.6 ± 13.6 g) and to most previous estimates of age-adjusted mass of brant Goslings. Thus, our results are consistent with the hypothesis that poor gosling growth is negatively influencing the brant population. There are 2 non-mutually exclusive explanations for the apparent growth ra...
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intercolony variation in growth of black brant Goslings on the yukon kuskokwim delta alaska
Journal of Wildlife Management, 2011Co-Authors: Thomas F. Fondell, Paul L Flint, James S Sedinger, Christopher A. Nicolai, Jason L. SchamberAbstract:ABSTRACT Recent declines in black brant (Branta bernicla nigricans) are likely the result of low recruitment. In geese, recruitment is strongly affected by habitat conditions experienced by broods because gosling growth rates are indicative of forage conditions during brood rearing and strongly influence future survival and productivity. In 2006–2008, we studied gosling growth at 3 of the 4 major colonies on the YukonKuskokwim Delta, Alaska. Estimates of age-adjusted gosling mass at the 2 southern colonies (approx. 30% of the world population of breeding black brack) was low (gosling mass at 30.5 days ranged 346.7 ± 42.5 g to 627.1 ± 15.9 g) in comparison to a third colony (gosling mass at 30.5 days ranged 640.0 ± 8.3 g to 821.6 ± 13.6 g) and to most previous estimates of age-adjusted mass of brant Goslings. Thus, our results are consistent with the hypothesis that poor gosling growth is negatively influencing the brant population. There are 2 non-mutually exclusive explanations for the apparent growth ra...
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Intercolony Variation in Growth of Black Brant Goslings on the
2011Co-Authors: Yukon-kuskokwim Delta, Paul L Flint, James S Sedinger, Christopher A. Nicolai, Thomas F. Fondell, Jason L. SchamberAbstract:Recent declines in black brant (Branta bernicla nigricans) are likely the result of low recruitment. In geese, recruitment is strongly affected by habitat conditions experienced by broods because gosling growth rates are indicative of forage conditions during brood rearing and strongly influence future survival and productivity. In 2006-2008, we studied gosling growth at 3 of the 4 major colonies on the Yukon- Kuskokwim Delta, Alaska. Estimates of age-adjusted gosling mass at the 2 southern colonies (approx. 30% of the world population of breeding black brant) was low (gosling mass at 30.5 days ranged 346.7 � 42.5 g to 627.1 � 15.9 g) in comparison to a third colony (gosling mass at 30.5 days ranged 640.0 � 8.3 g to 821.6 � 13.6 g) and to most previous estimates of age-adjusted mass of brant Goslings. Thus, our results are consistent with the hypothesis that poor gosling growth is negatively influencing the brant population. There are 2 non-mutually exclusive explanations for the apparent growth rates we observed. First, the population decline may have been caused by density-independent factors and habitat capacity has declined along with the population as a consequence of the unique foraging feedback between brant and their grazing habitats. Alternatively, a reduction in habitat capacity, as a result of changes to the grazing system, may have negatively influenced gosling growth, which is contributing to the overall long-term population decline. We found support for both explanations. For colonies over habitat capacity we recommend management to enhance foraging habitat, whereas for colonies below habitat capacity we recommend management to increase nesting productivity. 2011 The Wildlife Society.
Gilles Gauthier - One of the best experts on this subject based on the ideXlab platform.
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climatic effects on the breeding phenology and reproductive success of an arctic nesting goose species
Global Change Biology, 2008Co-Authors: Mariehelene Dickey, Gilles Gauthier, Mariechristine CadieuxAbstract:Climate warming is pronounced in the Arctic and migratory birds are expected to be among the most affected species. We examined the effects of local and regional climatic variations on the breeding phenology and reproductive success of greater snow geese (Chen caerulescens atlantica), a migratory species nesting in the Canadian Arctic. We used a long-term dataset based on the monitoring of 5447 nests and the measurements of 19 234 Goslings over 16 years (1989–2004) on Bylot Island. About 50% of variation in the reproductive phenology of individuals was explained by spring climatic factors. High mean temperatures and, to a lesser extent, low snow cover in spring were associated with an increase in nest density and early egg-laying and hatching dates. High temperature in spring and high early summer rainfall were positively related to nesting success. These effects may result from a reduction in egg predation rate when the density of nesting geese is high and when increased water availability allows females to stay close to their nest during incubation recesses. Summer brood loss and production of young at the end of the summer increased when values of the summer Arctic Oscillation (AO) index were either very positive (low temperatures) or very negative (high temperatures), indicating that these components of the breeding success were most influenced by the regional summer climate. Gosling mass and size near fledging were reduced in years with high spring temperatures. This effect is likely due to a reduced availability of high quality food in years with early spring, either due to food depletion resulting from high brood density or a mismatch between hatching date of Goslings and the timing of the peak of plant quality. Our analysis suggests that climate warming should advance the reproductive phenology of geese, but that high spring temperatures and extreme values of the summer AO index may decrease their reproductive success up to fledging.
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Feeding Ecology of Greater Snow Goose Goslings in Mesic Tundra on Bylot Island, Nunavut, Canada
The Condor, 2007Co-Authors: Benoît Audet, Gilles Gauthier, Esther LÉvesqueAbstract:AbstractAlthough mesic tundra is a habitat commonly used by arctic-nesting geese, their feeding ecology in this habitat is little known compared to wetlands. Our objectives were to determine the diet and food selection of Greater Snow Goose (Chen caerulescens atlantica) Goslings in relation to the nutritional quality of plants growing in mesic tundra habitats on Bylot Island, Nunavut, Canada. We used two different but complementary approaches: examination of esophageal contents of sacrificed wild Goslings, and direct observation of the feeding activity of captive, human-imprinted Goslings. The latter method was innovative and provided a reliable description of the diet, with results comparable to those obtained from wild Goslings. Although mesic habitats have a more diverse floristic composition than wetlands and sparse graminoid cover, Gramineae were preferentially selected and dominated the diet (~50%). The rest of the diet consisted mainly of members of the Juncaceae, Polygonaceae, and Leguminosae families. The diet of very young Goslings was diverse, but as they aged and gained efficiency, they concentrated on a few taxa. Goslings ate mostly leaves (~80%), but flowers (~20%) were also important. Food selection was influenced by nitrogen and total phenolic compounds content of plants, but the ratio of phenolic compounds to nitrogen in plant organs was most determinative of food choice. Neutral detergent fiber content of plants did not influence plant selection. Both plant nutritional quality and availability determined gosling diet across different mesic habitats and growing Goslings appeared to maximize their intake of metabolizable proteins.
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Gosling Growth and Survival in Relation to Brood Movements in Greater Snow Geese (Chen Caerulescens Atlantica)
The Auk, 2006Co-Authors: Julien Mainguy, Gilles Gauthier, Jean-françois Giroux, Joël BêtyAbstract:Abstract Post-hatch brood movements to high-quality foraging sites are common in precocial birds but may entail costs for young. We assessed effects of overland movements of broods between the nesting and rearing areas in Greater Snow Geese (Chen caerulescens atlantica) breeding on Bylot Island, Nunavut, Canada, to determine whether these movements affected gosling survival and growth. We monitored 51 radiomarked females over five years to quantify movement distance, movement duration, and gosling survival. Gosling growth was compared over four years using a sample of web-tagged broods recaptured shortly before fledging among adults that (1) nested and reared their young in a dense colony, (2) left the colony and moved ≈30 km to reach the main brood-rearing area, or (3) nested and reared their young in the main brood-rearing area. Brood movements by radio-marked birds were highly variable (2.6-52.5 km, depending on rearing areas used) and fairly rapid (≤6 days after hatch for 72% of the females). Gosling survival was not related to distance moved between nesting and brood-rearing areas. However, gosling growth was influenced by areas used and whether or not they had to move to reach their brood-rearing area. Geese nesting at the main brood-rearing area generally reared heavier and larger Goslings than those that moved ≈30 km from the main nesting colony to rear their brood at the main brood-rearing area. On the other hand, Goslings leaving the nesting colony after hatch were heavier and larger than those that stayed there throughout brood rearing in one of two years. Although brood movements allow Goslings access to high-quality habitats, they entail some costs. Thus, minimizing such movements through nest-site selection should provide a selective advantage by allowing Goslings to maximize their growth. Croissance et Survie des Oisons en Relation avec les Déplacements des Familles chez Chen caerulescens atlantica
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Natural infection by intestinal cestodes: variability and effect on growth in Greater Snow Goose Goslings (Chen caerulescens atlantica)
Canadian Journal of Zoology, 2002Co-Authors: Mohamed Righi, Gilles GauthierAbstract:We determined the species of intestinal helminths in Greater Snow Goose (Chen caerulescens atlantica) Goslings and examined annual variability in infection levels over a 5-year period on Bylot Island, Nunavut. The intestines of 112 wild Goslings collected when near fledging were examined. We also evaluated the effect of intestinal parasites on growth and behaviour of captive Goslings in a controlled experiment. In 2000, one group (n = 11) was treated with anthelmintic drugs (Piperazine 52 for nematodes and Droncit® for cestodes) and the other (n = 14) was used as a control. Four hymenolepidid cestodes were identified: Drepanidotaenia lanceolata, Hymenolepis barrowensis, Microsom acanthus setigera, and Retinometra longivaginata. No nematodes were detected. Prevalence of intestinal cestodes in wild Goslings was 100% but their abundance varied among years (from 28.9 ± 2.7 to 175.2 ± 49.7 (mean ± SE) cestodes per host) and individuals. Captive Goslings treated with anthelmintic drugs were free of parasites, w...
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the effect of wind radiation and body orientation on the thermal environment of greater snow goose Goslings
Journal of Thermal Biology, 2000Co-Authors: Daniel Fortin, Jacques Larochelle, Gilles GauthierAbstract:Abstract 1. Using four heated taxidermic mounts of Greater Snow goose Goslings of different ages (3–30 d), we found that exposure to wind (up to 5 m/s) or artificial radiation (up to 500 W/m 2 ) could change the standard operative temperature of gosling mounts by up to −20 or +18°C, respectively. 2. These values could vary by as much as 9°C due to the interaction between wind and radiation, or to changes in body orientation with respect to both these variables. In the presence of wind, radiative heat gain was reduced, and the interaction was generally more important when wind was perpendicular to the incoming radiation. 3. Predictive equations based on these results can be used to estimate the standard operative temperature of Goslings in the field and their ability to modify their thermal environment by changing orientation with respect to wind and sun.
Robert F Rockwell - One of the best experts on this subject based on the ideXlab platform.
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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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rapid environmental degradation in a subarctic ecosystem influences resource use of a keystone avian herbivore
Journal of Animal Ecology, 2012Co-Authors: Kristopher J Winiarski, Scott R Mcwilliams, Robert F RockwellAbstract:Summary 1. Environmental degradation can change resource use strategies of animals and thereby affect survival and fitness. Arctic herbivores may be especially susceptible to the effects of such environmental change because their rapid growth rates demand high-quality forage, which may be limited as environmental conditions deteriorate. We studied the consequences of a trophic cascade, driven by Lesser Snow Goose (Chen caerulescens caerulescens) overgrazing on the south-west coast of Hudson Bay, Canada, which has caused tidal marsh (TM) degradation and the reduction in highquality forage plants, on gosling growth and resource use. 2. We compared resource use and body size of Goslings that inhabited tidal and freshwater marsh (FM) to determine how current foraging strategies influence growth and to test the hypothesis that during early growth Goslings require and so consume high-quality TM plants, but that during later growth they may switch to foraging in lower-quality FM. 3. To investigate gosling resource use throughout growth, we measured once a week for 28 days the body size of Goslings as well as stable isotope ratios (d 34 S, d 15 N and d 13 C) in multiple tissues of Goslings that were collected from both TM and nearby FM. We also measured the stable isotope ratios in forage plants sampled along transects and from gosling foreguts. We used an isotopemixing model to determine the contribution of FM plants to gosling tissues. 4. Contrary to the proposed hypothesis, Goslings inhabiting FM or TM primarily consumed FM plants during early growth. Furthermore, Goslings that foraged extensively in FM had similar growth rates and grew to a similar size and body mass, as Goslings that foraged in the degraded TM. However, Goslings that currently inhabit freshwater or TM were significantly smaller than Goslings that inhabited TM in the 1980s prior to habitat degradation. 5. Consequences of smaller overall body size include decreased survival and fecundity for arcticnesting geese. The ability of phenotypically plastic responses to sustain persistence is limited by reaction norms and the extent of environmental change. Current research is assessing whether those limits have been reached in this system.
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Body condition and gosling survival in mass-banded lesser snow geese
The Journal of Wildlife Management, 1993Co-Authors: Tony D. Williams, Evan G Cooch, Fred Cooke, Robert F RockwellAbstract:Mass-banding of geese may disrupt family groups, at least temporarily, and could potentially affect survival of Goslings. Thus, we assessed the importance of changes in gosling body condition to prefledging gosling mortality and family group structure following mass-banding in the lesser snow goose (Chen caerulescens caerulescens), at La Perouse Bay, Manitoba, 1984-91. Mean observed brood size decreased (P < 0.01) in all years following banding for all observed broods (by 29-94%) and for resighted individuallymarked broods (by 33%). Banded broods also were smaller (P < 0.001) than non-banded broods after banding drives in two of 4 years (by 23-28%). Brood-mixing and adoption, following banding, were not common (occurring in a minimum of 2% of broods)
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Body Size Variation in Lesser Snow Geese: Environmental Plasticity in Gosling Growth Rates
Ecology, 1991Co-Authors: Evan G Cooch, Robert F Rockwell, David B. Lank, A. Dzubin, F. CookeAbstract:We examined the influence of timing of reproduction and brood size on growth rates of Goslings of nidifugous Lesser Snow Geese (Anser caerulescens caerulescens) using data collected at La Perouse Bay, Manitoba from 1978 to the present. Gosling growth rates declined significantly during the season, and the declines were independent of the parental genotype. Goslings from larger broods grew significantly faster, but there was no significant annual variation in the seasonal growth rate patterns with either hatch date or brood size. The hatch date and brood size effects could not be accounted for by systematic differences in either egg size or body size of the female parent. Goslings that grew more slowly due to the effects of hatch date or brood size were significantly smaller as adults. Because gosling growth rates influence final adult size, they may have a significant effect on various life history traits in this species.
Mark S. Lindberg - One of the best experts on this subject based on the ideXlab platform.
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environmental influence on life history traits growth survival and fecundity in black brant branta bernicla
Ecology, 1995Co-Authors: James S Sedinger, Paul L Flint, Mark S. LindbergAbstract:We studied relationships between body size of female Black Brant Goslings (Branta bernicla nigricans) late in their growth period and first year survival, eventual adult body size, breeding propensity, and size and volume of clutches they eventually produced to examine the relationship between growth and fitness in this population. We indexed body size by calculating PC1 scores based on either culmen and tarsus, or culmen, tarsus, and mass. Gosling (PC scores based on culmen and tarsus) size was positively correlated with resighting rate (P = 0.005), indicating that larger Goslings survived at a higher rate than did smaller Goslings. Gosling size was correlated with adult size of the same individuals (P = 0.0004). Larger Goslings were more likely to breed as 2- or 3-yr-olds than were medium or small Goslings (P = 0.008). Larger adult brant laid more eggs (P = 0.03) and produced clutches with greater total volume (P = 0.03) than did smaller brant. Given the important role of foraging environment in growth of Goslings, these data suggest an important role of early environment in determining life-history traits.
Evan G Cooch - One of the best experts on this subject based on the ideXlab platform.
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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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Fledging size and survival in snow geese: Timing is everything (or is it?)
Journal of Applied Statistics, 2002Co-Authors: Evan G CoochAbstract:In many birds, body size at fledging is assumed to predict accurately the probability of subsequent survival, and size at fledging is often used as a proxy variable in analyses attempting to assess the pattern of natural selection on body size. However, in some species, size at fledging can vary significantly as a function of variation in the environmental component of growth. Such developmental plasticity has been demonstrated in several species of Arctic-breeding geese. In many cases, slower growth and reduced size at fledging has been suggested as the most parsimonious explanation for reduced post-fledging survival in Goslings reared under poor environmental conditions. However, simply quantifying a relationship between mean size at fledging and mean survival rate (Francis et al ., 1992) may obscure the pattern of selection on the interaction of the genetic and environmental components of growth. The hypothesis that selection operates on the environmental component of body size at fledging, rather than the genetic component of size per se, was tested using data from the long-term study of Lesser Snow Geese ( Anser c. caerulescens ) breeding at La Perouse Bay, Manitoba, Canada. Using data from female Goslings measured at fledging, post-fledging survival rates were estimated using combined live encounter and dead recovery data (Burnham, 1993). To control for the covariation between growth and environmental factors, survival rates were constrained to be functions of individual covariation of size at fledging, and various measures of the timing of hatch; in all Arctic-breeding geese studied to date, late hatching Goslings grow significantly more slowly than do early hatching Goslings. The slower growth of late-hatching Goslings has been demonstrated to reflect systematic changes in the environmental component of growth, and thus controlling for hatch date controls for a significant proportion of variation in the environmental component of growth. The relationship between size at fledging, hatch date and survival was found to be significantly non-linear; among early hatching Goslings, there was little indication of significant differences in survival rate among large and small Goslings. However, with increasingly later hatch dates, there was progressively greater mortality selection against smaller, slower growing Goslings in most years. This would appear to suggest that body size matters, but not absolutely; small size leads to reduced survival for late-hatching Goslings only at La Perouse Bay. Since at least some of the variation in size among Goslings for a given hatch date reflects genetic differences, this suggests selection may favour larger size at fledging, albeit only among late-hatching Goslings.
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Body condition and gosling survival in mass-banded lesser snow geese
The Journal of Wildlife Management, 1993Co-Authors: Tony D. Williams, Evan G Cooch, Fred Cooke, Robert F RockwellAbstract:Mass-banding of geese may disrupt family groups, at least temporarily, and could potentially affect survival of Goslings. Thus, we assessed the importance of changes in gosling body condition to prefledging gosling mortality and family group structure following mass-banding in the lesser snow goose (Chen caerulescens caerulescens), at La Perouse Bay, Manitoba, 1984-91. Mean observed brood size decreased (P < 0.01) in all years following banding for all observed broods (by 29-94%) and for resighted individuallymarked broods (by 33%). Banded broods also were smaller (P < 0.001) than non-banded broods after banding drives in two of 4 years (by 23-28%). Brood-mixing and adoption, following banding, were not common (occurring in a minimum of 2% of broods)
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Body Size Variation in Lesser Snow Geese: Environmental Plasticity in Gosling Growth Rates
Ecology, 1991Co-Authors: Evan G Cooch, Robert F Rockwell, David B. Lank, A. Dzubin, F. CookeAbstract:We examined the influence of timing of reproduction and brood size on growth rates of Goslings of nidifugous Lesser Snow Geese (Anser caerulescens caerulescens) using data collected at La Perouse Bay, Manitoba from 1978 to the present. Gosling growth rates declined significantly during the season, and the declines were independent of the parental genotype. Goslings from larger broods grew significantly faster, but there was no significant annual variation in the seasonal growth rate patterns with either hatch date or brood size. The hatch date and brood size effects could not be accounted for by systematic differences in either egg size or body size of the female parent. Goslings that grew more slowly due to the effects of hatch date or brood size were significantly smaller as adults. Because gosling growth rates influence final adult size, they may have a significant effect on various life history traits in this species.
