A central focus of the research conducted in my lab is the study of 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.  And we are studying the payoff to females for choosing brightly colored males, particularly whether females might be receiving good-genes benefits from such choice.

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.

A second focus of my lab group 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 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 putatively made by Ivory-billed Woodpeckers, but we have yet to capture a photograph or video image clear enough to definitively prove the existence of this rare woodpecker.  Our work on the Ivory-billed Woodpecker continues mostly through setting automated cameras.

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After several years of failed attempts to get definitive evidence for the existence of ivorybills in Florida with field crews and personnel living on site, we now search with automated cameras that are tended four times per year.

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Studies of House Finches 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.  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 former 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.  I’m looking for graduate students and postdocs to join our team conducting tests for good genes.

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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 student 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.

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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.

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Last Revised: September 2009