Why Do Birds Sing?

My daughters have recently become obsessed with Elinor Wonders Why on PBS Kids. The theme song for the show includes the line, "Elinor wonders why, why do birds sing and how do they fly?" That line has been stuck in my head and playing on repeat for the last few days. So in a quest to answer Elinor's question about why birds sing I went back in my archives and found a couple of helpful explanation.  Why do birds sing? And how do they learn the songs that they sing? The answers to those...