ABS 2023
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The Role of Testosterone in Song Learning for a Species with a Two-Song Repertoire
Rebecca A Hill, Bernard Lohr. University of Maryland Baltimore County, Baltimore, Maryland, United States

Song is a learned behavior in oscine passerines, and song development must be accomplished correctly for a bird to reproduce successfully. Songs are memorized during an early sensory phase, then produced and modified throughout a sensorimotor phase during a bird’s first breeding year. In most species this learning period ends with crystallization, when the song becomes stereotyped. Crystallization is typically preceded by a rise in circulating testosterone. The role of testosterone in song learning for species with multiple song types is still unclear. We studied song learning in grasshopper sparrows, which have two distinct song types. We implanted a subset of birds with testosterone early during the sensorimotor phase and analyzed their recorded vocalizations during this period to determine each individual’s crystallization date. Our results revealed that early testosterone seems to accelerate learning; birds with implants completed the crystallization process, and did so 8-10 weeks earlier than control birds. This outcome contrasts with previous evidence suggesting that testosterone may function to arrest learning, potentially resulting in an abnormal crystallized song.