SciCombinator

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Concept: Chen

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1. 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. 2. 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. Since 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. 3. 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. 4. 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. 5. 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. 6. We show that events occurring both at and away from the breeding ground can affect the demography of migratory birds, either directly or through carry-over 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. This article is protected by copyright. All rights reserved.

Concepts: Affect, Chen, Snow Goose, Climate, Population, Climate change, Hunting, Demography

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Quantifying spatial patterns of bird nests and nest fate provides insights into processes influencing a species' distribution. At Cape Churchill, Manitoba, Canada, recent declines in breeding Eastern Prairie Population Canada geese (Branta canadensis interior) has coincided with increasing populations of nesting lesser snow geese (Chen caerulescens caerulescens) and Ross’s geese (Chen rossii). We conducted a spatial analysis of point patterns using Canada goose nest locations and nest fate, and lesser snow goose nest locations at two study areas in northern Manitoba with different densities and temporal durations of sympatric nesting Canada and lesser snow geese. Specifically, we assessed (1) whether Canada geese exhibited territoriality and at what scale and nest density; and (2) whether spatial patterns of Canada goose nest fate were associated with the density of nesting lesser snow geese as predicted by the protective-association hypothesis. Between 2001 and 2007, our data suggest that Canada geese were territorial at the scale of nearest neighbors, but were aggregated when considering overall density of conspecifics at slightly broader spatial scales. The spatial distribution of nest fates indicated that lesser snow goose nest proximity and density likely influence Canada goose nest fate. Our analyses of spatial point patterns suggested that continued changes in the distribution and abundance of breeding lesser snow geese on the Hudson Bay Lowlands may have impacts on the reproductive performance of Canada geese, and subsequently the spatial distribution of Canada goose nests.

Concepts: Canada, Branta, Canada Goose, Chen, Goose, Snow Goose, Geese, Anser

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Brachyspira is associated with diarrhea and colitis in pigs, and control of these pathogens is complicated by their complex ecology. Identification of wildlife reservoirs of Brachyspira requires the discrimination of colonized animals and those simply contaminated through environmental exposure. Lesser snow geese (Chen caerulescens caerulescens) were sampled in the Canadian arctic during the summer of 2011, and cloacal swabs were cultured on selective media. Brachyspira isolates were obtained from 15/170 (8.8 %) samples, and 12/15 isolates were similar to isolates previously recovered from pigs, including “Brachyspira hampsonii”, a recently characterized species associated with dysentery-like disease in pigs in North America. A pilot inoculation study with one strongly β-hemolytic B. hampsonii isolate resulted in fecal shedding of the isolate by inoculated pigs for up to 14 days post-inoculation, but no severe clinical disease. Results of this study indicate that lesser snow geese can be colonized by Brachyspira strains that can also colonize pigs. Millions of lesser snow geese (C. caerulescens caerulescens) travel through the major pork-producing areas of Canada and the USA during their annual migration, making them a potential factor in the continental distribution of these bacteria.

Concepts: United States, Ross's Goose, Bacteria, Anser, North America, Chen, Snow Goose, Canada

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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.

Concepts: Hunting, Population, Chen, Bird, Snow Goose, Demography, Immune system, Population ecology