Manly birds dress boldly
The saga of barn-swallow research is a bit like a soap opera; you think you鈥檝e seen the episode before, but if you look closely, there鈥檚 an intriguing twist to the tale.
Scientists using the birds as a window on evolutionary biology have found to their surprise that by artificially enhancing the color of male barn swallows鈥� breast feathers, the males attracted more (and more faithful) females than their duller-chested counterparts: The artificial color also triggered increased levels of the male hormone testosterone sharply and quickly in the 鈥渆nhanced鈥� birds, at a time in the breeding process when levels ordinarily would be falling.
Researchers had long known that internal chemistry determined the intensity of plumage color. And the team鈥檚 previous work had shown the effects of plumage on the males鈥� breeding success and the relative fidelity of female barn swallows to their beau. This was the first time anyone had shown, in effect, that putting on the Ritz could affect a male bird鈥檚 internal chemistry. As the team鈥檚 lead researcher, University of Colorado ecologist Rebecca Safran, explains, 鈥渢he experiment didn鈥檛 just improve the male鈥檚 looks in the eyes of females, it actually changed their body chemistry.鈥�
The new results suggest that testosterone levels may be closely tied to a male barn swallow鈥檚 color and fitness, adds Kevin McGraw, an Arizona State University researcher and member of the research team. The results appear in this week鈥檚 issue of the journal Current Biology.
