It’s a long-held tenet of avian biology that songbirds have just two types of a key reproduction hormone, gonadotropin-releasing hormone (GnRH), and only one actually triggers a seasonal “puberty” each spring in preparation for reproduction. But the new research shows a third form of the hormone, called lamprey GnRH-III-like hormone because it was first identified in lampreys, is also present in songbird brains.
November 17, 2003