Scientists call this phenomenon the dawn chorus, and they think it has to do with clarity of the sound. When the sun rises, it heats the ground and, in turn, the air. As the day goes on, the warm air rises, mixes with layers of cool air, and creates atmospheric turbulence, lots of pockets of air molecules moving around at different speeds. This turbulence interferes with the birdsong broadcast, making the sound less clear. Since male songbirds of the same species can sing slightly different versions of the same song, clarity is key, if a guy wants to set himself apart from the others and make sure he reaches the ladies. And it’s easiest to send a clear, complex message in the morning, when there’s not much atmospheric turbulence. Plus, singing in the morning means that a male songbird not only survived the night, but he has the time and energy to sit and sing, instead of foraging for breakfast right away.