Divergence across island populations in a region can occur rapidly when signals, such as the learned songs of birds, act as behavioral barriers to gene flow. We conducted a comparison of male songs in grasshopper sparrows (Ammodramus savannarum) across several island populations in the Caribbean, including Jamaica (A. s. savannarum) and Bonaire/Curacao (A. s. caribaeus). Grasshopper sparrow males sing two distinct songs: an insect-like “buzz” song and a “warble” song. Birds also sing a combination song (buzz followed by warble) when transitioning between these songs. Buzz songs in the Caribbean consisted of one or two brief introductory notes followed by a longer, rapidly-modulated sequence of very brief notes or note complexes, followed by a final short note. By analyzing the spectral and temporal components of buzz songs, we determined how songs varied across and within islands. We were able to distinguish key differences between songs and singing patterns based on geographical origin. Each Caribbean subspecies has a typical buzz song type (although A. s. savannarum has two) and songs are individually distinctive. A. s. caribaeus (the rarest subspecies studied) have the most distinct songs. Their songs showed the most rapid modulation rate, the least inter-individual variation, and these birds sang the combination song type almost exclusively. Our findings reveal distinctive differences in song structure across the Caribbean islands, and future work will compare these Caribbean songs to the songs of several grasshopper sparrow subspecies on mainland North America.