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  • 1
    Online Resource
    Online Resource
    Cary :Oxford University Press, Incorporated,
    Keywords: Birds -- Conservation -- America. ; Birds -- Migration -- America. ; Birds -- Ecology -- America. ; Birds -- Habitat -- America. ; Electronic books.
    Description / Table of Contents: The apparent decline in numbers among many species of migratory songbirds is a timely subject in conservation biology, particularly for ornithologists, ecologists, and wildlife managers. This book is an attempt to discuss the problem in full scope. It presents an ambitious, comprehensive assessment of the current status of neotropical migratory birds in the U.S., and the methods and strategies used to conserve migrant populations. Each chapter is an essay reviewing and assessing the trend from a different viewpoint, all written by leaders in the fields of ornithology, conservation, and population biology.
    Type of Medium: Online Resource
    Pages: 1 online resource (506 pages)
    Edition: 1st ed.
    ISBN: 9780195359176
    DDC: 598.252/5/097
    Language: English
    Note: Intro -- Contents -- Introduction: Importance of Knowledge and its Application in Neotropical Migratory Birds -- PART I: POPULATION TRENDS -- 1 Population Trends from the North American Breeding Bird Survey -- 2 The Strength of Inferences about Causes of Trends in Populations -- PART II: TEMPORAL PERSPECTIVES ON POPULATION LIMITATION AND HABITAT USE -- 3 When and How are Populations Limited? The Roles of Insect Outbreaks, Fire, and Other Natural Perturbations -- 4 Summer versus Winter Limitation of Populations: What are the Issues and What is the Evidence? -- 5 Habitat Requirements During Migration: Important Link in Conservation -- 6 Habitat Use and Conservation in the Neotropics -- PART III: FOREST MANAGEMENT -- 7 Impacts of Silviculture: Overview and Management Recommendations -- 8 Effects of Silvicultural Treatments in the Rocky Mountains -- 9 Silviculture in Central and Southeastern Oak Pine Forests -- PART IV: GENERAL HUMAN EFFECTS -- 10 Effects of Agricultural Practices and Farmland Structures -- 11 An Assessment of Potential Hazards of Pesticides and Environmental Contaminants -- 12 Livestock Grazing Effects in Western North America -- PART V: SCALE PERSPECTIVES -- 13 Habitat Fragmentation in the Temperate Zone -- 14 A Landscape Ecology Perspective for Research, Conservation, and Management -- 15 Ecology and Behavior of Cowbirds and their Impact on Host Populations -- 16 Single-Species versus Multiple-Species Approaches for Management -- 17 Summary: Model Organisms for Advancing Understanding of Ecology and Land Management -- Index -- A -- B -- C -- D -- E -- F -- G -- H -- I -- K -- L -- M -- N -- O -- P -- R -- S -- T -- W.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 15 (1999), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We recorded the blows of gray whales during their southbound migration past central California in January 1994, 1995, and 1996, using thermal imaging sensors. For our sampling purposes, we defined day (0730–1630) and night (1630–0730) to coincide with the on/off effort periods of the visual counts being conducted concurrently. We pooled data across the three years of sampling and tested for diel variation in surfacing interval, pod size, offshore distance, migration rate, and swimming speed by comparing paired day/night means for samples collected within the respective 24-h period. We performed these tests using data from the entire migration period and then repeated the tests for samples collected prior to and after the approximate median migration date (15 January). Over the entire migration period we observed larger diurnal pod sizes (x̄day= 1.75 ± 0.280, x̄night= 1.63 ± 0.232) and greater diurnal offshore distances (x̄day= 2.30 ± 0.328 km, x̄night= 2.03 ± 0.356 km) but found no diel variation in surfacing interval. For the entire migration period, the nocturnal migration rate (average number of whales passing per hour) was higher than the diurnal rate. During the first half of the migration we detected no diel variation in pod size or surfacing interval, but diurnal offshore distances were larger than at night (x̄day= 2.28 ± 0.273 km, x̄night= 1.96 ± 0.318 km). Diurnal and nocturnal migration rates prior to 15 January were not different. During the second half of the migration, there was no diel variation in surfacing interval, pod size, or distance offshore, but the nocturnal migration rate was higher (28%, SE = 11.6%) than the diurnal rate. We found no diel variation in swimming speed in any comparison. We propose that later migrants socialize more during the day, which effectively slows their diurnal rate of migration relative to nocturnal rates.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 2 (1988), S. 37-50 
    ISSN: 1573-8477
    Keywords: Nest predation ; open nesting birds ; assemblage organization ; apparent competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The addition of nest predation as a major process to current theories of space utilization and coexistence of open-nesting bird species adds predictive power to hypotheses of resource partitioning and organization of species assemblages. Nest predation can influence the organization of assemblages if predators respond to nests in a density-dependent manner and if predators specialize on nest types. Evidence shows that nest predation is commonly density-dependent and that predators can specialize on nest types. Consequently, nest predation can select for coexistence of bird species that nest at different heights and in different microhabitats (i.e. partitioning of nesting space) to minimize density-dependent responses of predators to the accumulating densities of species within similar nest sites. I establish a series of predicted patterns (1) to test whether predation is operating to influence partitioning of space and coexistence of species, (2) to distinguish effects of nest predation from competition, and (3) to determine the mechanism by which nest predation acts to organize assemblages. Using published and unpublished data to test the predictions, nest predation is seen as a process that we can no longer afford to ignore.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 380 (1996), S. 338-340 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Competition for food is often assumed to be the cause of esource partitioning, but the risk of nest predation can theoretically increase with overlap in resource (nest site) selection, and thereby favour resource partitioning among coexisting species6"12. The risk of nest predation may increase ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 66 (1985), S. 563-573 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Resource selection is a function of interactions of organisms (competition, predation) as well as characteristics of the resource and organisms. I provide a quantitative model that integrates these factors. I use the model to predict profitability of fruits to tropical birds, but the model and its predictions are applicable to a wider array of systems and organisms. Profitability of a fruit is determined by rewards provided by the pericarp (mass and caloric yields) relative to costs (metabolic requirements, handling time, search time, behavioral interference, predator avoidance) associated with finding and eating that fruit (Fig. 1). Fruits increase in profitability with increases in fruit size until increases in handling time offset increases in pericarp mass. The fruit size at which increases in handling time offset increases in pericarp mass varies among bird species due to differences in bill and body size. Decreases in feeding rate due to decreasing numbers of fruits and increasing search time causes reduced profitability and this effect becomes more severe with decreasing fruit size and/or increasing frugivore size. Consequently, as fruit size decreases relative to frugivore size, fruit abundance becomes increasingly important to fruit selection by frugivores. However, while profitability of resources is a function of characteristics of the resources and the organisms, biological interactions can change profitability rankings; resources that may be more profitable in the absence of behavioral interference, exploitation competition, or predation risk can become less profitable in the face of these interactions. The proposed model integrates these interactions to provide predictions of resource selection and these predictions are supported by published studies.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Island size, habitat heterogeneity, and distance from major (“mainland”) stands of habitat were examined relative to composition and number of coexisting reptile species dependent on upland habitats of 11 mountain and 4 riparian habitat islands. Species richness increased with area on mountain islands, but area was unimportant in predicting species richness on riparian islands. Instead, isolation was of primary importance. Regardless of factors determining species richness, composition of species were deterministic; small assemblages were always totally included subsets of all larger assemblages. This pattern of determinism apparently reflects selective extinctions and the inability of species to recolonize due to the insurmountable barrier imposed by the Sonoran Desert.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2013-07-31
    Description: [1]  The transport of sand in saltation is driven by the persistently unsteady stresses exerted by turbulent winds. Based on coupled high-frequency observations of wind velocity and sand flux on a desert dune during intermittent saltation, we show here how observations of saltation by natural winds depend significantly on the time scale and method used for determining shear stress and sand flux. The correlation between sand flux and excess shear stress (stress above a threshold value) systematically improves for longer averaging time scale, T , and is better for stress determined by the law-of-the-wall versus the Reynolds stress method. Fitting parameters for the stress-flux relationship do not converge with increasing T , which may be explained by the non-stationary nature of wind velocity statistics. We show how it may be possible, based on the scale-dependent statistics of stress fluctuations, to re-scale saltation flux predictions for wind observations made at different timescales. However, our observations indicate hysteresis and time lags in thresholds for initiation and cessation of saltation, which complicate threshold-based approaches to predicting sediment transport at different time scales.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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