This grant provides funds for the purchase of electronic equipment for precise analysis of sounds. The equipment will first be used by Dr. Trainer to answer questions about characteristics of bird song that may be important in the female's choice of a mate. According to one model of the evolution of female mating preferences, females who choose older males have longer-lived offspring, and this causes preferences for traits that indicate a male's age to increase in frequency. This mechanism is likely to be important in long-tailed manakins, because males of this species do not reproduce until they are at least nine years old, and only a few of the mature males attract most of the females. Male manakins attract females through a unique and puzzling cooperative display: two reproductively mature males sing and dance together, yet only one male mates. Dr. Trainer's previous research showed that pairs of males that have well-coordinated songs receive more visits by females than those with uncoordinated songs. Dr. Trainer now will examine the relationship between age and song coordination in this unusual display. She will perform a precise acoustic analysis of the songs of males of known relative age, in order to answer three questions: (1) Do females prefer well-coordinated songs? (2) Are older males more able to coordinate with the partner and to sing in a consistent manner? (3) Does song coordination improve through learning as a male adjusts his song to match his partner's? This study will increase our understanding of the role of individual development in sexual selection of male characteristics and the evolution of female mating preferences.
