Date of Award
8-14-2020
Document Type
Dissertation
Degree Name
Environmental Sciences, Ph.D.
First Advisor
Thomas Risch
Committee Members
James Kennon; Ron Johnson; Tanja McKay; Virginie Rolland
Call Number
LD 251 .A566d 2019 M45
Abstract
The broad array of colors represented in avian eggshells has promoted extensive investigations into its evolutionary significance. Although many hypotheses exist that explain conspicuous egg colors, including egg recognition against brood parasitism, protection from UV rays, and thermoregulation, they fail to adequately explain the adaptive function of vivid blue eggs. The Sexually Selected Egg Color Hypothesis (SSECH) states that blue-green eggshell coloration is a post-mating, sexually selected signal that conveys female quality, and male birds that observe more pigmented eggs would increase their care accordingly, resulting in higher quality chicks. Using a population of eastern bluebirds (Sialia sialis) in northeast Arkansas from 2007–2009, I investigated potential predictors of blue-green eggshell variation (clutch size, clutch imitation day, temporal trend), and I examined the relationship between egg blue-green color and maternal quality (scaled-body-mass index, age, feather color, and clutch initiation day) in a subset of banded females. For females captured multiple times throughout the study, I compared interclutch eggshell coloration between consecutive clutches of each nesting season across years. To tests the effect of egg color saturation on male care, I conducted a double swap (whole clutches of eggs and whole broods of chicks) experiment between the palest and darkest clutches in the sample, then investigated whether fledging success or chick quality could be predicted by eggshell coloration. My results suggest biliverdin is not a limited pigment and is highly consistent across years, and further suggest egg color does not reflect female quality. I found no evidence that males increase their parental care when exposed to darker blue-green eggs, which is the major tenet of the SSECH. However, I did find that males increased their visits if they received their original chicks back. Additionally, egg color did not predict fledging success, chick body-mass index, or chick immunocompetence. Overall, my findings suggest eastern bluebirds did not evolve blue-green egg color as a sexually selected trait. As part of the GK12 NSF fellowship I received, I used my results to design a model to elucidate scientific processes to 6th–8th grade students that teachers can use by establishing a bluebird colony at their school.
Rights Management
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
McKie-Voerste, Annabelle, "A Test of the Sexually Selected Egg Color Hypothesis in Eastern Bluebirds (Sialia Sialis)" (2020). Student Theses and Dissertations. 373.
https://arch.astate.edu/all-etd/373
