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Document Type

Dissertation - University Access Only

Award Date

2013

Degree Name

Doctor of Philosophy (PhD)

Department

Natural Resource Management

First Advisor

Kenneth F. Higgens

Abstract

Recent climate change modeling predicts future climates in many areas of the world will be warmer, and that these areas may experience more frequent extreme weather events. If egg size, like clutch size, is affected by environmental conditions during the nesting season then production and regional duck populations may also be affected because larger eggs result in larger ducklings which experience higher survival rates than smaller ducklings. The effect of past climate variability on North American duck species has not been addressed prior to this research. This study provides empirical baseline data on current, recent, and historic duck egg size metrics from measurements conducted in the United States and Canada during recent field research (N=36,775 eggs) and from measurements of museum specimens (N=30,762) of 34 wild North American duck species. These egg metrics were obtained from eggs collected or measured on site at various locations in Canada or the United States from 1859-2010. Digital calipers were used to obtain maximum egg length and width/breadth (± 0.01 mm) for fresh (incubated) eggs in field studies and from intact (blown) egg shells in museum collections. Egg volume (cm3) was estimated using the equation [0.51*LW2] (Hoyt 1979). Average egg size metrics (mean and standard deviations) for 67,537 eggs have been synthesized, cataloged and compared to previously published measurements for each species. Runt eggs, which are less than 75% of the mean egg volume for a species, were documented for 28 duck species, of which five species had not previously been reported. Total occurrence of runt eggs was 0.78% in the entire dataset (N=67,537), and varied by species from 0-8.7%. A set of a-priori generalized additive models were used to explore the correlations between egg metrics (i.e., length, width, and volume) and spring (March, April and May) weather, Palmer Drought Severity Index values, EPA ecological region, and year. Egg volume of 82% of the 34 duck species studied were significantly different between years, 82% varied due to average monthly weather conditions, 67% varied between ecological regions, and 73.5% varied relative to Palmer Drought Severity Index values. The results of this study indicate that wild duck egg size varies through time and across geographic regions, and also suggests that egg size variability is related to changes in environmental conditions.

Library of Congress Subject Headings

Ducks--Climatic factors--North America
Ducks--Eggs--North America
Duck populations--North America

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

278

Publisher

South Dakota State University

Rights

Copyright © 2013. Julie R. Delong. All rights reserved.

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