My research focuses on the evolution of colorful plumage.  In the nineteenth century, Charles Darwin and Alfred Wallace first recognized the challenge that brightly colored plumage posed to the theory of evolution by natural selection.  Why would small vulnerable creatures like songbirds be brilliantly and conspicuously colored?  The existence of colorful plumage presented one of the strongest challenges to natural selection theory.

Darwin proposed and argued for the idea that female mate choice drives the evolution of colorful plumage.  Wallace rejected this idea and proposed various forms of natural selection - crypsis, mimicry, and species recognition - to explain colorful plumage.  Until the late 1980s, however, the ideas of Darwin and Wallace remained largely untested.  My research program picks up where Darwin and Wallace left off.  My students and I are experimentally testing the role of female mate choice and male-male competition in the evolution of various types of ornamental plumage.  We are also studying the proximate control of variation in expression of colorful plumage to better understand the signal content of such ornamental display.

A major thrust of my research program is aimed at understanding the function and evolution of the three types of ornamental coloration of feathers: carotenoid pigmentation, melanin pigmentation, and structural coloration.  We currently focus our studies on three locally common species of birds - House Finches, American Goldfinches, and Eastern Bluebirds. House Finches have carotenoid-based coloration; American Goldfinches have both carotenoid-based and eumelanin-based ornamental coloration; and Eastern Bluebirds have both structural blue and rust phaeomelanin coloration.  Lab associates also study fish coloration. Follow the links below for brief descriptions of ongoing research projects.

A second focus of my students and me is the conservation of birds of the southeast.  I am part of a research team undertaking a study of the ecology of encephalitis viruses in Alabama and my team's focus in this large multi-PI project is to inventory birds and study the relationship between occupancy by various species and key habitat variables.  A primary goal of this work is to build predictive models whereby presence of birds would be predicted vegetation parameters and ultimately from satellite images showing vegetation.

In May 2005 with Brian Rolek and Tyler Hicks, I discovered a population of Ivory-billed Woodpeckers in northwest Florida.  Dan Mennill and his research team joined me and my students in a project to definitively document Ivory-billed Woodpeckers.  We have recorded numerous sounds puatively made by Ivory-billed Woodpeckers but we have yet to capture a photograph or video image clear enough to definitvely prove the existence of this rare woodpecker.  Our work on the Ivory-billed Woodpecker continues.

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The glamour bird gets all the attention.  I’m currently working on a project to document, determine the breeding status of, and delimit the distribution of Ivory-billed Woodpeckers in the Choctawhatchee River Basin on the Florida panhandle.  My partner in this work since the beginning of our research effort has been Dan Mennill, my former postdoc now an assistant professor at the University of Windsor in Ontario.  During the winter and spring 2005/2006 we found many large cavities, unique feeding trees, heard kent calls or double raps on 41 occasions, and observed ivorybills 14 times.  We even captured one or more birds on video, although the video is of very poor quality.  My master's student, Brian Rolek, is the field leader of the team searching for Ivory-billed Woodpeckers in Florida.  See the Auburn and Windsor Ivorybill web pages for a detailed account of evidence gathered to date.

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Studies of House Finches and American Goldfinches build on substantial previous work in which we showed that male carotenoid-based plumage coloration is an honest signal of male condition that is used by females in choosing mates. Early studies were summarized in a book in 2002.  In recent studies with Dr. Wendy Hood I have tested the relative importance of various environmental challenges during molt on color expression as well as the potential for interactive effects of these variables to affect coloration.  In future research Wendy and I will conduct field correlative studies looking at factors that affect expression of carotenoid and melanin pigmentation during molt.  Wendy and her graduate students will also be collaborating with my bird group on determinants of carotenoid and melanin coloration in bluegill sunfish.

In addition to the research investigating the effect of environmental challenges on color production, with master’s student Kristal Huggins and Dr. Mary Mendonca, I am testing whether the large doses of carotenoids needed to produce ornamental coloration might have a toxic effect on colorful birds.  For birds on high and low carotenoid diets we are measuring steroid hormones indicative of stress, oxidative stress, muscular condition and muscular physical performance.

My interest in plumage coloration and disease led to a collaboration with Dr. Scott Edwards, a population geneticist at the Harvard University. My doctoral student, Susan Balenger, and Scott's postdoc Dr. Camille Bonneaud are leading a collaborative study on gene expression in House Finches following exposure to the bacterial pathogen Mycoplasma gallicepticum (MG).  Our long-term goal is to conduct a true test of the good genes hypothesis by assessing gene expression following parasite exposure in well-ornamented and poorly ornamented males. 

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A major focus of my research concerns the function and evolution of structurally based blue plumage coloration. Current research on structural coloration of the Eastern Bluebird is being conducted by my doctoral student, Mark Liu, and my master's students Rusty Ligon and Austin Mercadante..  Much of this research focuses on testing the hypothesis that the structurally based blue coloration of bluebirds might serve as a condition-dependent signal of quality like carotenoid-based coloration. So far, we have found that plumage blueness is positively related to nest box acquisition and feeding rate of males but that the blue coloration of males does not appear to be an object of female choice. We are currently testing the relative importance of genes and environment on expression of plumage blueness and looking at mate guarding and male paternity in relation to plumage blueness. In collaboration with my former postdoc, Dr. Herman Mays, Mark Liu is assessing the relative importance of ornamentation versus genetic compatibility in mate choice in the bluebird.  Mark will look at mating patterns related to both structural blue coloration and genetic complementarily and will assess the fitness of offspring produced by ornamented males versus males that were genetically compatible with their mates. Austin Mercadante will be testing the role of orange and blue coloration in contests between males.  Rusty Ligon will focus on the coloration of young bluebirds in juvenal plumage.  In particular, Rusty will be testing the idea the bold spots of young bluebirds functions as a signal of age.                  
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Master’s student, Camille Okekpe, who work both in my lab and the lab of Dr. Mary Mendonca is studying the hormonal mechanisms responsible for the regulation of primary offspring sex-ratio in the Zebra Finch.  Females (being the heterogametic sex) are capable of using preovulatory mechanisms to skew offspring sex-ratio in response to changes in diet and/or maternal condition.  In further investigation of this phenomenon Camille is manipulating zebra finch diet to determine if there is an associated significant difference in circulating progesterone and corticosterone hormone levels that affect primary offspring sex-ratio.

Last Revised: September 2006