We know that even relatively small populations of great tits can harbour hundreds of different song types. But how does this diversity compare with that found across larger geographic areas? And what can the answer to this question tell us about the forces that shape bird song? We are curating a large dataset that will allow us to answer these questions in unprecedented detail. This is a collaboration with Sara Keen and the Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology.