Birds use sounds to communicate, and large amounts of information are transmitted by vocalizations. We summarized the current research progress on the relationship between bird vocal behavior and individual fitness including individual status (physical parameters, hormone levels and health conditions), social status and reproduction (sexual selection and breeding success). We found that the relationships between song traits and single physical parameter were different according to the traits examined. Bird vocalization could be regulated by various hormones, and related with the individuals' social ranks. Both male and female songs are related with reproduction, but there are differences in the strategies of parents’ vocal behavior. The effect of vocalization on reproductive fitness is also influenced by other factors, such as taxa and mating system. The biological information represented by bird vocalization is a comprehensive manifestation of individual body condition, and its influence on individual fitness is more complicated. In order to interpret the biological information represented by vocalizations, we need to consider multiple parameters from multiple prospects, such as social grade, physical condition and reproduction.