Since the work of Marler in 1970, songbirds have become a choice model to study language-related processes in the brain, and especially the lateralization of these processes. Among songbirds, starlings appear as a good model for the study of lateralization because they offer a variety of songs with different social functions. In order to investigate the central processing of communicative sounds in starlings, neuronal responses to a variety of artificial nonspecific and behaviorally-relevant species-specific stimuli were recorded in both hemispheres of awake and anesthetized birds. Quantitative assumptions about the electrophysiological characteristics of different brain nuclei could be formulated thanks to a new extensive approach that we developed to record a large number of single units. Recordings were made in the primary auditory area of the songbird brain, namely the Field L Complex, which is the main auditory input of the song system, and in the vocal control nucleus HVC, which is a highly integrative part of this system. In both cases, the right hemisphere showed significantly more responsive units than the left one when the birds were awake, and this difference was reduced or even suppressed under anesthesia. Most importantly, our results showed a complex and state-dependent hemispheric specialization towards behaviorally-relevant classes of stimuli. These results are reminiscent of previous studies made on other sensory systems. They support the idea that the two hemispheres exhibit different general functions in terms of attention or the nature of the cognitive task performed, and add to the many parallels between the avian and human systems that have become paradigmatic of vocal communication.