"In some species, if a female bird hears a male of the species sing, her ovaries grow faster and she will lay more eggs," Bentley said.
In addition, tape-recorded songs from a male can trigger a rapid increase in testosterone of another male defending his territory, a phenomenon Wingfield has studied for many years.
In either case, the brain detects an external cue birdsong that triggers a physical or behavioral response, possibly both. Just how the responses are transmitted through the nervous system is unknown, Wingfield said. But finding a third form of GnRH in areas of the brain that produce and process birdsong holds the potential for ultimately identifying how cues such as song can be directly translated into hormone output that affects reproduction.
It could be the first step in showing that the hormone is released directly into the bloodstream from the song centers of the brain, rather than going through the hypothalamus, Wingfield said.
"We've never had a link like this for the GnRH-type molecule in these brain areas that produce and process birdsong," he said. "The fact that it's there is unique to higher vertebrates."
The researchers note the importance environment can play in reproductive responses. For instance, previous studies have shown testosterone levels in the saliva of sports fans increases when their teams win, and it decreases when their teams lose. Likewise, the widely recognized home-field advantage in sports has recently been correlated to a higher salivary testosterone level in home-team players than in visitors.
But at a time when people are increasingly concerned about environmental changes, the researchers say, there is still very little information about how organisms respond to changes in various triggers temper
'"/>
Contact: Vince Stricherz
vinces@u.washington.edu
206-543-2580
University of Washington
17-Nov-2003