Birds sing the most around an hour before dawn, when the air is at its stillest. Theoretically, this enables sounds to travel further, making song up to 20 times more effective than if sung at midday. It’s a good time to take a moment to soak in the spring birdsong and notice the individual harmonies blending together. International Dawn Chorus Day brings casual bird appreciators, ornithological experts and dedicated twitchers together in a celebration of birdsong. In our series, experts give their insights on nature’s chorus. The dawn chorus is beautiful anywhere, but your local birdsong may sound rather different to nearby areas. Even in the same neighbourhood, birds of the same species don’t always sound exactly alike. I was recently teaching undergraduates about bird song, and they recorded blue tits singing around campus. The students found plenty of differences between individual birds. Some blue tits sang their classic song, which sounds a bit like they are saying “ he-llo, I’m a little blue tit ”.…