This year I am determined to know their voices, these birds we live with early and late and which come to us without cost or solicitation. Up early today I hear the first sounds of morning and quickly visit the "bird jam" site I've found ("know the birds you hear").
It is the cardinal who leads the way, at least today. It is the cardinal up early and singing his heart out. What wakes the first bird? What character of creation gives dawn this soundtrack, makes it so that — before we see, taste, smell or feel morning — we hear it?
I read that birds sing most during mating season and often from a high perch, that cardinals sing year round, and that some birds, larks for instance, sing while flying.
As for the larger question, I'll turn to literature rather than science: "Why do birds sing in the morning?" said British author Enid Bagnold, author of National Velvet. "It's the triumphant shout. We got through another night!"