How do tropical birds decide when to sing? Scientists know that increasing daylight triggers brain changes that prompt spring singing in northern birds. But day length in the tropics hardly varies. Do the brains of tropical birds show similar seasonality? Apparently they do. Researcher Ig-nacio Moore of Virginia Tech and colleagues write in a recent issue of the Journal of Neuroscience that they studied two populations of Rufous-collared Sparrows living on either side of the Ecuadorian Andes. Western birds started singing in August, and eastern birds started in November. The "neural song control system" in their brains also changed seasonally, growing by about 50 percent during the periods the high-altitude-dwelling birds sang.
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