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Document Type

Thesis - University Access Only

Award Date

1994

Degree Name

Master of Science (MS)

Department

Wildlife and Fisheries Science

First Advisor

W. Carter Johnson

Abstract

Blue jays (Cyanocitta cristata L.) are important predators on and dispersers of nuts of oaks and other Fagaceous trees in eastern North America. Acorns comprise much of the jay diet (Beal 1896), especially during the autumn months when jays may consume or cache a significant portion of an acorn crop. However, jays do not appear to possess physiological adaptations for countering the protein-binding properties of secondary compounds (tannins) found in the acorns of many oak species. I examined responses by blue jays to a mixture of infested and uninfested pin oak (Ouercus palustris Muenchh.) acorns to see if jays selectively consumed nuts containing weevil larvae (Curculio) as a protein supplement to a high-tannin, all-acorn diet (see Johnson et al. 1993. Oecologia 94:159-164). I also tested whether overwinter caching reduced tannin levels in northern red oak (Quercus rubra L.) and bur oak (Ouercus macrocarpa Michx.) acorns, making them more digestible to the jays. Acorns were X-rayed to determine infestation status and then offered to individual jays in an aviary setting. Jays handled and consumed non-infested nuts significantly more often than infested nuts, and proportional use of infested nuts did not increase during continued exposure to a high tannin diet. Acorns in simulated caches did not differ significantly in tannin level from uncached acorns, and jays lost body mass rapidly on both cached and uncached acorn diets. Thus, my results were not consistent with my original hypotheses: jays did not make extensive use of weevil-infested nuts and caching did not appear to improve the quality of an all-acorn diet

Library of Congress Subject Headings

Blue jay--Nutrition--Requirements
Acorns as food
Tannins
Protein binding

Description

Includes bibliographical references (pages 92-98)

Format

application/pdf

Number of Pages

110

Publisher

South Dakota State University

Rights

Copyright © 1994 Mark Dixon. All rights reserved.

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