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The wings of many ducks are decorated with intense bands of color, while others are downright drab. Have you ever stopped to think about the significance behind the coloration of birds? Biologist Kevin McGraw has.
McGraw’s laboratory in the School of Life Sciences at Arizona State University delves deep into research that examines pigments and structural color and their link to nutrition in birds – with funding from the National Science Foundation (NSF) and support from postdoctoral fellow Melissah Rowe and University of Rochester undergraduate Alison Ossip-Klein.
McGraw’s research grows out of his interest in understanding how and why animals display the colors that they do. In previous work, for example, he discovered that foods rich in carotenoids – yellow, orange and red pigments found in plants that also function as antioxidants – can directly affect bird coloration and health.
“These studies of carotenoids and color have emerged as an excellent model for testing life-history tradeoffs using a common nutritional currency,” McGraw says.
McGraw’s most recent NSF study examines how pigments in ducks play a role in their vision, health and appearance. McGraw’s group is working with 120 male and female ducks from two waterfowl species; the Mallard (Anas platyrhynchos) and the Northern Pintail (Anas acuta). As part of the experimental regime, the ducks are first fed a low-carotenoid “depletion diet” to flush their systems of these pigments. Then they are divided into six groups and placed on experimental diets that differ only in concentration of xanthophyll carotenoids (like lutein and zeaxanthin, typical yellow components of corn). Once the birds molt and develop their attractive adult colors this fall, McGraw and his team will score coloration, immune system performance and carotenoid accumulation in internal body tissues (like ovaries and eyes) to determine how relatively important these different uses of pigments are.
Ossip-Klein joined McGraw's laboratory by applying to do a summer Research Experiences for Undergraduates (REU) fellowship funded by the federal government and administered in the College of Liberal Arts and Sciences by the School of Life Sciences. “I never worked with birds before, but was curious about sexual selection and coloration in animals and found the topic interesting,” Ossip-Klein says. She was in charge of diet preparation and contributed to regular blood draws (for health assessment) and behavioral monitoring.
“We typically work with ten or more ASU undergraduates in our research each year,” McGraw says. “They become involved through many different routes – as student volunteers, to earn independent-study credit, as hired employees on grants, or as part of our formal research track, the School of Life Sciences Undergraduate Research (SOLUR) program.” To ensure the best fit in his lab, McGraw searches for students “with diverse interests, perhaps having a background in ecology, evolution or physiology or an interest in animal communication, sexual selection, coloration or immunology”.
Ossip-Klein gained a range of skills and experiences working with the ducks, including learning how to handle birds, conducting morphological measurements and video analysis of animal behaviors, and utilizing sophisticated biochemistry equipment, like High Performance Liquid-Chromatography (HPLC), to analyze pigments in food and tissue.
Ossip-Klein also made time during her 11-week stay in Arizona to conduct her own independent project. McGraw says that “it was my and Melissa Rowe’s hope that we could attract a student that would not only assist with our project but also have the maturity and drive to pursue his/her line of research with these birds.” Ossip-Klein chose to explore the role of carotenoids in influencing the flight capacity of ducks. Based on similar work in the field, she hypothesized that ducks exposed to higher concentrations of carotenoids would fly higher and faster. She will be analyzing the data she’s gathered over the course of the next few months.
“Kevin definitely has one of the top labs in the country that deals with animal coloration,” says Australia native Melissah Rowe. Rowe was drawn to McGraw's lab while completing her doctorate at the University of Chicago. McGraw gave a talk there about on colors in songbirds in 2005, and she introduced herself and was soon collaborating with him.
“Understanding the potential tradeoffs of a certain molecule for multiple functions within an organism, and how an organism might prioritize an allocation to one or the other of those competing functions,” is what Rowe says is the most interesting part of this research in McGraw’s laboratory.
Rowe also points out, “Kevin is a very prolific researcher, and is one of the main reasons I chose to come to ASU.”
By: Addie Lenox
School of Life Sciences
Media contact: Margaret Coulombe