DescriptionWhile early auditory experience establishes the initial organization of the auditory system, cortical plasticity in adulthood enables the organism to adapt an ever-changing environment. The adult auditory system needs to maintain perceptual filters for efficient processing of native stimuli while, at the same time, being ready to respond to novel exemplars and sound categories if they are encountered. The importance of this juxtaposition of stability with plasticity is highlighted in adult learners of a second language who learn to process a novel category of sounds while still maintaining efficient coding for their native language. In the present study, we simulated the foreign immersion experience by exposing zebra finches, a socially gregarious songbird species, to passive playback of either conspecific aviary sounds or heterospecific aviary sounds. After different exposure durations, multiple microelectrodes were placed bilaterally in an area of the bird’s auditory cortex, NCM, to record neural responses. The results of Experiment 1 revealed unexpectedly dynamic changes in the normal pattern of lateralization over time. In Experiment 2, birds were similarly exposed to conspecific and heterospecific environments for various times, and then were asked to perform a behavioral discrimination in an operant paradigm. Behavioral discrimination was significantly enhanced in a subset of birds with previous exposure to heterospecific sounds. Experiment 3 tested spectro-temporal receptive fields (STRFs) in single NCM neurons before and after exposing naïve birds to novel conspecific and heterospecific sounds. Results indicated that brief exposure to song stimuli was sufficient to produce detectable changes in STRFs, and the magnitude of these changes depended on the category of stimuli presented. In sum, the adult auditory cortex is capable of passively detecting and adapting to changes in the statistics of the auditory environment, while maintaining pre-established filters for species-specific vocalizations. Division of labor between hemispheres and/or between neuronal subtypes could underlie this ability to respond to both old and new categories of stimuli, providing both stability and plasticity. These results advance the understanding of adult plasticity, with potential implications for second language learning.