Research news: For barn swallows, feathers make the man, says CU-Boulder study

The News:
For barn swallows, feathers make the man, says CU-Boulder study
New study has implications for the ecology and evolution of wildlife signaling
University of Colorado at Boulder Assistant Professor Rebecca Safran of the ecology and evolutionary biology department retrieves a North American barn swallow from a mist net for marking and release.
A new study led by the University of Colorado at Boulder has shown the testosterone of male North American barn swallows skyrocketed early in the breeding season when their breast colors were artificially enhanced by researchers, indicating the clothes -- or in this case, the feathers -- make the man.
The swallows, whose breast feathers were darkened to a deep red known to be most attractive to females, likely had more testosterone racing through their bodies because of amorous interactions with the opposite sex and more run-ins with jealous males, said CU-Boulder Assistant Professor Rebecca Safran, lead study author. The jump in testosterone was unexpected because it was observed at the time in the breeding cycle when levels of sex steroids like testosterone are typically declining, she said.
"A simple change in appearance had striking physiological consequences for these barn swallow males, which was a big surprise," said Safran. "The experimental manipulation didn't just improve their looks in the eyes of the females, it actually changed their body chemistry. The relationship between a male's physiology and the traits that win him mates is a lot more flexible than we had imagined."
A paper on the subject is being published in the June 3 issue of Current Biology. Co-authors on the study include James Adelman and Michaela Hau of Princeton University and Kevin McGraw of Arizona State University. The two-year study was funded primarily by the National Science Foundation.
The new study is the first to show significant feedback between physical appearance and physiology in birds, and has implications for better understanding the ecology and evolution of physical signals such as feather color, she said. Read on...

The Research:
Read the research behind this story in the journal Current Biology.