Moore and University of Washington, Seattle, researchers John C. Wingfield in biology and Eliot A. Brenowitz in psychology, looked at seasonal changes in the brains of birds that account for their singing, which is a part of the male mating behavior. In the Nov. 10 issue of The Journal of Neuroscience (www.jneurosci.org/), the official journal of the Society for Neuroscience, they report that birds in high latitudes are driven to sing by seasonal changes in the length of the day, which causes changes in the song-control nuclei of the brain. However, in the tropics, where the day length does not vary much by season, the propensity for birds to sing still changes, but is driven by environmental cues that vary by locale -- a fact that could mean those birds are more susceptible to global warming than birds in higher latitudes.
Correct timing of breeding is necessary for reproductive success, Moore said. Research by others has shown that testosterone is the main physiological cue regulating seasonal changes in the neural song-control system. Seasonal changes in the song-control system have been demonstrated by other scientists in all northern latitude species that have been investigated. But no one had researched whether seasonal changes occurred in the brains of birds in tropical areas where day-length changes are minimal. "We think it's probably still testosterone that causes tropical birds to sing, but that the environmental cue is different," Moore said. The scientists wanted to determine whether "seasonal changes in brain structure can be mediated by l
Contact: Sally Harris