Master's Theses

Document Type

Thesis - campus only access

Date of Award

Fall 1974

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Charles A. Ely

Abstract

Brown-headed Cowbirds were studied in Ellis County, Kansas from February, 1973 to August, 1974. Objectives of the study were to 1) determine the frequency and effect of cowbird parasitism in a prairie habitat 2) determine adaptations of host species to parasitism and, 3) determine population structure and movements of cowbirds banded in Ellis County. One hundred and eleven of 520 nests of host species (21%) were parasitized. The frequency of parasitism varied from a low of 2.7 per cent (Say's Phoebe) to a high of 100 per cent (Cardinal). All but one grassland host species received moderate to heavy parasitism. Parasitized nests fledged one less host (.5 per nest) than non-parasitized nests (1.5 per nest). Only .3 cowbirds fledged per nest. Probable adaptations to parasitism were nesting prior to the cowbirds breeding season by Horned Larks, aggression by colonies of Red-winged Blackbirds, and nest desertion and removal of cowbird eggs by Lark Buntings. A total of 9,651 cowbirds were banded during this study. Adults departed from Ellis County by mid-August, whereas transient populations of immatures were present until November. Observations of color-marked individuals were reported near Buffalo, Oklahoma, Dodge City, Rush Center, and McCracken, Kansas.

Comments

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Rights

© 1974 Richard A. Hill

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