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J.R. Sauer

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Context: Reproduction is a critical component of fitness, and understanding factors that influence temporal and spatial dynamics in reproductive output is important for effective management and conservation. Although several indices of reproductive output for wide-ranging species, such as migratory birds, exist, there has been no theoretical justification for their estimators or associated measures of variance. Aims: The aims of our research were to develop statistical justification for an estimator of reproduction and associated variances on the basis of an existing national wing-collection survey and banding data, and to demonstrate the applicability of this estimator to a migratory game bird. Methods: We used...
Categories: Publication; Types: Citation; Tags: Wildlife Research
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Information on change in population size over time is among the most basic inputs for population management. Unfortunately, population changes are generally difficult to identify, and once identified difficult to explain. Sources of variald (patterns) in population data include: changes in environment that affect carrying capaciyy and produce trend, autocorrelative processes, irregular environmentally induced perturbations, and stochasticity arising from population processes. In addition. populations are almost never censused and many surveys (e.g., the North American Breeding Bird Survey) produce multiple, incomplete time series of population indices, providing further sampling complications. We suggest that each...
Categories: Publication; Types: Citation
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Population models have great potential as management tools, as they use infonnation about the life history of a species to summarize estimates of fecundity and survival into a description of population change. Models provide a framework for projecting future populations, determining the effects of management decisions on future population dynamics, evaluating extinction probabilities, and addressing a variety of questions of ecological and evolutionary interest. Even when insufficient information exists to allow complete identification of the model, the modelling procedure is useful because it forces the investigator to consider the life history of the species when determining what parameters should be estimated...
Categories: Publication; Types: Citation
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Two winter bird surveys in Canada have range-wide population monitoring potential: Christmas Bird Counts (CBCs) and Project FeederWatch (PFW). CBC trends are shown to be correlated to Breeding Bird Survey (BBS) trends, whether or not part of the winter range lies outside the CBC coverage area. Some species are poorly covered by this survey (e.g. seabirds, nocturnal species, and Neotropical migrants). Only eight Canadian breeding species that are not sampled by the BBS have their winter range well-covered by the CBC, but the CBC should be valuable as an independent source of trend data for many more species, including northern nesters with only marginal BBS coverage. More work is needed to show whether PFW trends...
Categories: Publication; Types: Citation
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