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Document Type

Thesis - University Access Only

Award Date

2001

Degree Name

Master of Science (MS)

Department

Wildlife and Fisheries Science

First Advisor

Kenneth F. Higgens

Abstract

Grassland bird populations have been declining throughout North America since the 1960’s. These declines have been attributed to landscape fragmentation, loss of grassland habitats, and the size and isolation of remaining grasslands. The purpose of this study was to inventory non-game birds on xeric mixed-grass prairies of various sizes in fragmented and non-fragmented landscapes of western South Dakota to determine what effects landscape fragmentation and grassland patch size have on avian (bird) communities. Avian species were surveyed within a randomly placed 150m x 120m fixed-width belt transect in 125 grasslands and 21 croplands throughout western South Dakota. Each study site was surveyed once between May 20 and July 5 in either 1999 or 2000. Grasslands ranged in size from 12.34 to 2,590 ha. Croplands ranged in size from 17.4-127.6 ha, and consisted of either row crop, small grain (winter wheat, flax) or idle/fallow fields. A total of 52 avian species were observed, of which were 19 grassland obligates, 18 facultative grassland species and 15edge/generalist species. Six species comprised >85% of the total birds observed; these were: grasshopper sparrows, western meadowlarks, brown-headed cowbirds, chestnut-collared longspurs, bobolinks and red-winged blackbirds. Grasshopper sparrows and western meadowlarks were observed in >99% of grassland patches. Avian community composition was affected by landscape fragmentation and grassland patch sizes. Chestnut-collared longspurs were more abundant in grasslands within non-fragmented versus fragmented landscapes. The grasshopper sparrow exhibited area-sensitivity, increasing in abundance with increasing patch size in fragmented landscapes. The brown-headed cowbird, a notorious edge species and nest parasite, was more abundant in small grasslands within fragmented landscapes than in grasslands within non-fragmented landscapes. Certain grassland birds were never observed in cropland while two species, lark buntings and horned larks, occurred most frequently in croplands. These results indicate that landscape fragmentation and resulting variability of patch sizes affects the avian species composition of grassland patches, and may result in higher abundance of generalist/edge species and corresponding lower abundance and productivity of grassland obligate species. Efforts to conserve grassland birds must take into account landscape fragmentation and resulting grassland patch size effects on grassland birds. Management priority should be placed on large grassland patches located in landscapes with high percentages of grassland to compensate for grassland patch size and fragmentation effects on grassland birds.

Library of Congress Subject Headings

Birds--Habitat--South Dakota
Bird populations--South Dakota
Fragmented landscapes--South Dakota
Grasslands--South Dakota

Description

Includes bibliographical references (pages 90-100)

Format

application/pdf

Number of Pages

123

Publisher

South Dakota State University

Rights

Copyright © 2001. Julie R. Delong. All rights reserved.

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