| Hill Lab Research |
| Research
interests |
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.
| Ivorybills |
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.
| House Finches and American
Goldfinches: environmental regulation of coloration |
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.
| Eastern Bluebirds: from nanostructure to
macrocolor |
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.
Back
to top
| Eastern Bluebirds: from offspring to parents |
| Zebra-Finches:
primary sex-ratio |
| 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. | ![]() |
| Arbovirus:
applied biology |
| 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. Art Appel, 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. So members of my lab group are gathering data on the relative abundance of all bird species in our encephalitis study areas. This is a novel approach to the study of the ecology of arboviruses. |
Last Revised: September 2006