"Next, I will explain the answer to your second question, 'why do birds sing so gay?' I spent a lot of time to study birds and insects. The answer is birds can sing at any time of day, but during the dawn chorus their songs are often louder, livelier, and more frequent. It’s mostly made up of male birds, attempting to attract mates and warn other males away from their territories."
https://rudymartinka.wordpress.com/2015/08/26/king-solomon-why-do-fools-fall-in-love/