All About Birds has posted some early recordings of songbirds, made 80 years ago today. These were among the very first bird recordings, a joint project of Fox-Case Movietone and Cornell's Arthur Allen. Since sound technology was still fairly new in 1929, the recordings are less sophisticated than ones made today. The link mentions the issue of microphones:
"Early microphones were not very sensitive," Budney explains. "You had to put the microphone right next to the bird. Today we can selectively record an individual with parabolas that amplify sound and directional microphones. In these ground-breaking recordings one also hears clicks, pops, and hissing, noise that was inherent in early recording systems. Even so, the Stewart Park recordings are remarkable for their time."At the link there are 80-year-old recordings of a Song Sparrow and a Rose-breasted Grosbeak. I find the Song Sparrow recording clearly recognizable but the grosbeak a bit more muddled.