Almost all songbird males develop fully crystallized songs before or during their first potential breeding season, when they use these important signals during interactions that determine their social success. We describe a rare phenomenon, in which vocal maturation is delayed until the second potential breeding season, or third year of life, in Yellow-rumped Caciques (Cacicus cela vitellinus) from lowland Panama. We heard predefinitive males in their second year sing only uncrystallized song, while three definitive males known to be in their third year sang fully developed songs matching the local dialect. The unusual system of polygynous breeding colonies in caciques may account for why vocal development is delayed. We would expect to find other examples of delayed vocal maturation in polygynous, nonterritorial species, in which second-year males have little opportunity for social success.