According to the Woodland Trust, this early singing is known as the dawn chorus, and it can start as early as 4 am and last for several hours. Birds do it to attract mates and warn other birds to avoid their turf. One theory as to why they opt for the wee hours to communicate these important messages is because the low visibility makes it hard to do other bird activities, like foraging. Keeping their activity level low, they opt to sing instead.

Another theory argues that birds use the morning vocals to project an image of strength. By singing with fervor, they’re letting other birds know they survived the night—no guarantee in nature—and would make for an excellent mate.

Like a good recording studio, the early morning hours also allow birds to transmit a clear tune thanks to the cooler, drier air. Because birds have distinctive chirps, that clarity helps them be more easily identified by birds within listening distance.