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I
am broadly interested in the optics, evolution and development of
animal colors, primarily those produced by highly organized tissues
(structural colors) in feathers. These tissues act as one, two and
three dimensional photonic crystals and are thus of interest both at a
fundamental and applied level. Some examples are shown below: |
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A TEM image of a barbule with a one-dimensional photonic structure (thin film) of melanin and keratin creating weak iridescence in the shiny cowbird Molothrus bonariensis. |
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A TEM image of a barbule with a two-dimensional, hexagonally-packed array of hollow melanin granules producing bright iridescent color in the wild turkey Meleagris gallopavo. |
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A TEM image of a barb with a three-dimensional matrix of keratin and air creating a non-iridescent color in eastern bluebird Sialia sialis. Click to play movie showing successive slices through the tissue.
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We use techniques including light microscopy, scanning and transmission electron microscopy, electron tomography and atomic force microscopy to examine the structure of these tissues and use optical modeling to determine how they create color. Recently, we have become interested in the ontogeny of biophotonic tissue, about which practically nothing is known. We are using these same techniques to examine developing feathers and will soon use some simple polymer chemistry to look for fundamental processes that may be involved. This line of research, along with phylogenetic mapping and reconstruction, should shed some light on how evolution has tweaked a few basic materials (keratin and melanin) to create the astonishing diversity of avian structural colors. My other research focus is on
antimicrobial
defenses of birds and bird-microbe interactions, another field of both
fundamental and applied interest. We have shown that both preen oil and
incubation have antimicrobial properties and are interested in their
modes of
operation as well as their evolutionary history and impact on avian
life
histories. We use protein assays, antimicrobial assays, molecular
methods and
some old-fashioned field work to test these ideas.
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