Population connectivity plays a pivotal role in shaping genetic and cultural diversity both within and among species. Birdsong is acquired through social learning and is transmitted across generations, exhibiting regional variations that contribute to our understanding of cultural evolution. As island colonising songbirds, silvereyes (Zosterops lateralis) are renowned for their rapid adaptation to new environments and hence are an excellent model taxon for comparing patterns of cultural evolution in populations with varying levels of connectivity. In this study, dialects of four silvereye populations in the South East Queensland region were compared, for which genetic relationships have been previously established. Dialect similarities were explored by developing representative repertoires from field recordings and extracting a number of acoustic parameters. Interestingly, no correlation between acoustic distance and either genetic or geographic distance was found, suggesting that cultural divergence likely arises through other processes. Evidence for acoustic convergence of island repertoires was also found. Analyses of spectral features revealed unique traits in island dialects, with higher mean frequency values observed despite expectations based on physiological constraints of the larger island silvereyes. Island sites were also distinguished by their greater repertoire similarities with each other and a higher syllabic diversity compared to mainland populations. These findings challenge our understanding of dialect evolution on islands and suggest potential acoustic adaptation to the environment. This sensitivity of dialect evolution to environmental conditions highlights the potential impacts of habitat disturbances or environmental changes on avian populations. The implications of these findings extend beyond the field of bioacoustics, underscoring the role of cultural evolution in shaping avian behaviours with implications for conservation, behavioural ecology, and evolutionary biology.