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:

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.


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.

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.

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.

Research

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.

The Shawkey Lab

With Jakob Vinther, Julia Clarke, Quanguo Li and others we have pioneered the reconstruction of the colors of fossil feathers using quantitative comparisons of the morphology of fossilized melanosomes, This research has already shown that complex color patterns in feathers existed before the origin of flight,  that penguin ancestors lacked the camouflaged counter shading found in modern penguins, and that iridescence was present in the basal paravian theropod Microraptor. We are continuing to refine our methods to detect the presence of structural colors in fossils and to expand them to include other vertebrate groups including mammals and squamates.

 

 




I encourage students interested in graduate work in my lab (either as a master's student or as a Ph.D. student) to contact me directly before applying.

reconstruction by Mick Ellison