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 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 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.

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Dr. Alex Badyaev has been a long-time collaborator with me.  Alex and I have also been working on variation in sexual dimorphism and selection on dimorphism across North America and particularly between our focal study populations in Montana and Alabama.  We have shown that males and females vary extensively and independently in size and shape across N. American populations, and that the sizes and shapes of males and females conform closely with the local optimum dictated by survival, fecundity, and pairing selection.  However, selection on adult phenotypes cannot achieve the observed degree of dimorphism evolution, so we have begun to look at ontogeny as a source of divergence in dimorphism among populations.  Most recently, Alex and I found that House Finch chicks in different positions in the hatch order grow and develop differently and that females in different populations allocate males and females to positions in the hatch order such that they create males and females that match the local optimum in size and shape.  We are now following up this study with a detailed investigation of maternal effects.

With Kristen Navara, a doctoral student who works jointly in my lab and in the lab of

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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 is being conducted by my doctoral students, Lynn Siefferman and Mark Liu, on the Eastern Bluebird, which has brilliant blue/UV coloration.  Lynn Siefferman’s work 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, she has found that plumage blueness is positively related to nest box acquisition and feeding rate of males. 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. 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.

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Stephanie Doucet, another doctoral student, is studying the function and evolution of elaborate male ornaments in Neotropical manakins.  Stephanie’s project investigates the causes and consequences of variation in ornamentation in Long-tailed Manakins.  Male manakins have elaborate, sexually selected black, red, and blue coloration that results from melanin pigments, carotenoid pigments, and structural elements, respectively. Stephanie is conducting careful observations of the leks of these birds to determine how plumage coloration affects male mating success.  Because these birds go through a long series of transitional plumage before attaining definitive plumage in their fifth year, Stephanie will also look at the ontogeny of the different color displays to gain insight into how the different components of plumage function.

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My doctoral student, Matt Shawkey, is studying feather color at a very small scale, examining the nanostructural basis of variation in coloration and the ways in which feather-degrading microbes might affect this color. In bluebirds, he has found a number of nanoscale morphological variables that predict color variation quite well.  Additionally, he has thoroughly characterized the microbial communities on their feathers and has shown that some of these microbes can disrupt feather morphology and cause drastic changes in color.  He has recently expanded these studies to species with carotenoid-based coloration.

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Although much of the research in my lab group focuses on plumage coloration, my students and I are also interested in the use of song as a signal of condition, especially relative to female choice of mates. With Dr. Dan Mennill, a postdoc in my lab, and Alex Badyaev, I am studying how song functions as a signal in a Montana population of House Finches.  This Montana population is particularly appropriate for such a study because Alex has detailed information on pairing success, nesting success, provisioning rate, extra-pair paternity etc. that can compared to song parameters.  Dan also studies the ecology and evolution of vocal duetting in neotropical Thryothorus wrens and female eavesdropping on male song contests in both temperate and tropical territorial songbirds.

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Dr. Herman Mays joined my lab group as a postdoc in 2001, and he helped us establish a molecular ecology lab where we can conduct genetic sexing, paternity analysis, and molecular systematics.  Herman is currently working with my former master's student, Michelle Beck (now at Washington State University), on an analysis of House Finch paternity, with my Ph.D. students, Lynn Siefferman and Mark Liu, on Eastern Bluebird paternity, and with my former master's students Barb Ballentine (now at Duke University) and Amber Keyser (recently finished her Ph.D. at the University of Georgia) on Blue Grosbeak paternity. Bill Ashwander, an undergraduate student at Auburn, has been working with Herman on a phylogeny of House Finch subspecies and populations using mitochrondrial DNA.  The genetic expertise that Herman brings to my research group has provided exciting new opportunities for the study of sexual selection, mating systems, and plumage coloration.

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Although I am primarily a behavioral and evolutionary biologist, I also have been involved in a number of applied projects looking at bird habitat use.  I am currently working on a study of the ecology of encephalitis virus in a swamp forest in Alabama. This research is being conducted with Dr. Ed Cupp, an entomologist at Auburn who is conducting companion sampling of the mosquitoes of this area, and Dr. Tom Unnasch, who is identifying the blood meals of mosquitoes.  A primary goal of this study is to identify the feeding preferences of bird-feeding mosquitoes, and this requires a null hypothesis based on random bird encounters. Toward this end, Laura Estep, a doctoral student in my lab, is using her skills in spatial ecology and geostatistics to create Kriged maps representing the abundances of all birds within the feeding range of mosquitoes.  From this spatial abundance data set, Laura will develop a model of mosquito movement and construct a null model for host feeding.  Laura’s null model can then be compared to observed blood-meal composition.  This is a novel approach to the study of the ecology of arboviruses and holds great promise for helping to better understand these diseases.

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Last Revised: January 2005