When Clark attended graduate school, his Ph.D. work focused on the roles of sexual selection and flight performance in shaping hummingbird tail morphology. In 2008, he published a paper titled "The Anna's Hummingbird Chirps With It's Tail," which received wide publicity and helped launch his current research focus. Clark's paper described how Anna's hummingbirds (Calypte anna) make a loud sound with their tail feathers during courtship displays rather than vocally.
After completing his doctorate, Clark and his advisor, Richard Prum, were awarded a grant from the National Science Foundation to study the physics of the sounds feathers make. Clark traveled to Latin America, where he recorded the courtship displays of a number of hummingbird species that produce distinctive sounds with their tail feathers including sheartails and woodstars. He then took his research into the lab, where he used a wind tunnel to reproduce the sounds feathers make when the birds are in flight in the wild, and studied how feathers produce sounds over a range of air speeds. [Research supported by National Science Foundation grant IOS 09-20353.] (Date of Image: unknown)
Credit: Christopher Clark, Yale University