Wrong on Song?

Talking of birds, it seems Darwin was wrong about their song - or rather, he over-generalised, and his generalisation, as is so often the case (especially with a revered name like Darwin), hardened into dogma, to the point where observers were obliged to overlook what their eyes and ears were plainly telling them - that female birds often sing as lustily as males. Or at least they do in Australia; when it comes to our own birds, Darwin's generalisation seems to hold true. None of this, of course, really addresses what is still essentially a mystery - why birds sing as they do, why some of them are capable of such astonishingly rich, varied and inventive song, why they devote so much of their time to it, and why we humans find this alien sound so affecting and meaningful. So profound is this mystery that the naturalist, philosopher and musician  David Rothenburg has devoted an entire book to it - Why Birds Sing. His researches lead him to believe that the simplest answer might be closest to the truth - that songbirds sing so extravagantly, dispensing round their magnanimity of sound, because (silence please) they enjoy it.