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2020 (1)

1972 (1)

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Book
Populations in a Seasonal Environment. (MPB-5)
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ISBN: 0691209642 Year: 1972 Publisher: Princeton, N.J., Baltimore, Md. : Princeton University Press, Project MUSE,

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Abstract

Most organisms live in a seasonal environment. During their life cycles, some species face seasons of cold and heat, aridity and abundant rainfall, migration and stable residence, breeding and nonbreeding. Populations grow and decline as supplies of materials essential to their survival wax and wane. Such qualitative truths as these flow obviously from field observations. In this original monograph, Stephen Fretwell analyzes the highly complex interaction between a population and a regularly varying environment in an attempt to define and measure seasonality as a critical parameter in the general theory of population regulation. Concerned primarily with the size and the habitat distribution of populations, Professor Fretwell develops simple models that, when applied to specific populations, usually of birds, demonstrate the effect of seasonal variations on the regulation of populations. He maintains that seasonality, as a concept, is essential to a full understanding of environmental interaction. During the course of his exposition, the author offers several new hypotheses, including theories affecting the breeding, numbers, distribution, and diversity of wintering birds, and a theory affecting the body size of sparrows.


Book
Some Adaptations of Marsh-Nesting Blackbirds. (MPB-14), Volume 14
Author:
ISBN: 0691209936 Year: 2020 Publisher: Princeton, NJ : Princeton University Press,

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Abstract

The variety of social systems among the New World blackbirds (Family Icteridae) and the structural simplicity of their foraging environment provide excellent opportunities for testing theorics about the adaptive significance of their behavior. Here Gordon Orians presents the results of his many years of research on how blackbirds utilize their marsh environments during the breeding season. These results stem from information he gathered on three species during ten breeding seasons in the Pacific Northwest, on Red-winged blackbirds during two breeding seasons in Costa Rica, and on three species during one breeding season in Argentina. The author uses models derived from Darwin's theory of natural selection to predict the behavior and morphology of individuals as well as the statistical properties of their populations. First he tests models that predict habitat selection, foraging behavior, territoriality, and mate selection. Then he considers some population patterns, especially range of use of environmental resources and overlap among species, that may result from those individual attributes. Professor Orianns concludes with an overview of the structure of bird communities in marshes of the world and the relation of these patterns to overall source availability in these simple but productive habitats.

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